Representing the unrepresentable: the Mosque of Córdoba and the ideal Islamic temple

Influential architects such as


Introduction
The importance of Leon Battista Alberti's De re aedificatoria (written between 1443 and 1452) cannot be overstatedit was the first architectural treatise written since antiquity that bridged the gap with classical architecture by recovering Vitruvius's De architectura and established the formal, aesthetic, and ideological foundations for Renaissance architecture.Crucially, it distilled some traditional traits of Classical architecture into an archetype that would have an enormous influence thereafter.In its seventh book, devoted to the 'ornament to sacred buildings', Alberti described an idealised temple that should be detached and 'free of any profane contamination; to this end it should address a large, noble square and be surrounded by spacious streets, or, better still, dignified squares, so that it is perfectly visible from every direction' and should be raised via a podium. 1 In terms of its shape, Alberti preferred the circle or some regular polygons that can be circumscribed by a circle since '[it] is obvious from all that is fashioned, produced, or created under her influence, that Nature delights primarily in the circle'. 2 The temple should also be hierarchically composed according to geometric and proportional rules: [Just] as the head, foot, and indeed any member must correspond to each other and to all the rest of the body in an animal, so in a building, and especially a temple, the parts of the whole body must be so composed that they all correspond one to another, and any one, taken individually, may provide the dimension of all the rest. 3re in general, the book reflected the key influence that Platonism and Neoplatonism had in the Renaissance through an understanding of architecture as a manifestation of pure and eternal ideas.Alberti's well-known definition of beauty -'Beauty is that reasoned harmony of all the parts within a body, so that nothing may be added, taken away, or altered, but for the worse.' 4 has been, arguably, the most forceful formulation of the idea that buildings should be perfect, finished, and stable.
Rudolf Wittkower, in his seminal book Architectural Principles in the Age of Humanism (1948), described Alberti's definition of the centrally planned temple as 'the first full program of the ideal church of the Renaissance'. 5Wittkower rebuilt its complex intellectual environment, permeated with both Classical and Christian thought, to firmly rebuke the, at the time, predominant interpretation of Renaissance as a purely aesthetic and mainly worldly and profane style.Renaissance artists, ' guided by Plato and the neo-Platonists and supported by a long chain of theologians from Augustine onwards', were 'convinced of the mathematical and harmonic structure of the universe and all creation'. 6The shape and proportions of Alberti's centralised churches were meant to act as a symbolic apparatus mediating between the microcosm and the macrocosm, and between man and God: 'For them the new forms of the Renaissance church embodied sincere religious feeling no less than did the Gothic cathedral for the mediaeval builder.' 7 While, during Renaissance, very few centralised plan churches were built, Wittkower showed how Alberti's theorisation permeated the work of Filarete, Francesco di Giorgio, Bramante, Leonardo da Vinci, Serlio, Giuliano da Sangallo, and Palladio.This idealised type was also beautifully rendered in paintings such as Perugino's The Delivery of the Keys (c.1482) (Fig. 1), Raphael's Marriage of the Virgin (1504), and The Ideal City of Urbino (c.1480).The latter is an anonymous painting attributed to a variety of artists including Alberti himself, which matches his description remarkably well.These depictions usually show the churches in the middle of wide squares, as isolated objects that can be seen from any direction.Summarising, Alberti's centralised temple is hierarchical and assembled from heterogenous parts according to strict compositional rules; it is closed, stable, and has solid tectonics (stressing its perfection and transcendence).Furthermore, it is a free-standing and convex object (hence, better understood from its outside), and its finite form, defined by significant limits, conveys a meaning.
It should be noted that most of these traits could be found in Western architecture since antiquity, but Alberti, by distilling them into an idealised formulation that brought together Classical Humanism and Christianity, established the canon of what could be called the 'Western architectural object', the influence of which extended well beyond the Renaissance age and sacred architecture.In fact, while architecture and the ideas it conveys have obviously changed enormously since then, it could be argued that many of the most influential buildings of the last century still followed said archetype, albeit in a secularised way, from Gunnar Asplund's Stockholm Public Library to Frank Lloyd Wright's Guggenheim Museum, Le Corbusier's Villa Savoye, Mies van der Rohe's Crown Hall, to OMA's Casa da Música, to name just a few (Fig. 2).Even today, most Western buildings still comply with many of its traits.

The hypostyle mosque as anti-object
While the subject of this text is a specific Islamic architectural type, the hypostyle mosque, and its differences with an (also specific) Western canon, it is important to clarify some general facts dealing with Islamic art, 8 a term that, according to Jonathan Bloom and Sheila Blair, is difficult to define and is 'used somewhat differently than such comparable terms as "Christian" or "Buddhist" art: Islamic art refers to the arts of all Islamic cultures and not just the arts related to the religion of Islam'. 9Furthermore, Islamic art is also difficult to generalise since it shows a great historical and regional variety: 'It is easier to say what Islamic art is not that what it is.Unlike such terms as "Renaissance" or "Baroque", "Italian" or "French", Islamic art refers neither to art of a specific era nor to that of a particular place or people.' 10 Nonetheless, there are universal and constant principles that stem from Islamic ideology, spirituality, and jurisprudence (fiqh, ‫ﻓ‬ ‫ﻘ‬ ‫ﻬ‬ ) that endow Islamic art and architecture with a unique and recognisable identity. 11t should also be pointed out that, while many Western buildings contradict or deviate from the Albertian canon, there are Islamic buildings that do comply with it remarkably well, including some particularly famous like the Dome of the Rock (690-692) or the Taj Mahal (1631-1653) (Fig. 3).That is however not the case with hypostyle mosques which have long captured the attention of Western architects due to their significant differences with European paradigms.In 1986, Christian Norberg Schultz noted: 'The hypostyle mosque, thus, is in principle an "open" form, where spatial elements could be added or taken away without destroying its meaning.' 12 He stressed how this fundamentally contradicted Alberti's definition of 'classical composition'.In his 1997 text From Object to Field, Stan Allen put forward the term 'field condition' as an alternative architectural paradigm opposed to the objects of 'classical architecture'.
Field configurations are loosely bounded aggregates characterised by porosity and local interconnectivity.The internal regulations of the parts are decisive; overall shape and extent are highly fluid.Field conditions are bottom-up phenomena: defined not by overarching geometrical schemas but by intricate local connections. 13ile he related their growing popularity with contemporary developments (such as mathematical field theory, non-linear dynamics, or the shift from analogue to digital) and mentioned precedents in twentieth-century visual arts and music, he singled out the Mosque of Córdoba (Fig. 4) as the earliest and most important example of a long genealogy of 'fields'. 14Allen also cited Alberti's definition of beauty and his description of 'classical architecture' is coherent with his canon: Parts form ensembles which in turn form larger wholes.Precise rules of axiality, symmetry or formal sequence govern the organisation of the whole.Classical architecture displays a wide variation on these rules, but the principle of hierarchical distribution of parts to whole is constant. 15ilding on a previous analysis of the Mosque of Córdoba by Rafael Moneo, 16 Allen stressed how its structure of ten identical double tiered arcades and the resulting grid of columns form an 'undifferentiated but highly charged field […] The axial, processional space of the Christian church gives way to a non-directional space, a serial order of "one thing after another".' 17The system estab-   lished in the original mosque remained unchanged in the subsequent expansions: 'The relations of part to part are identical in the first and last versions constructed.The local syntax is fixed, but there is no overarching geometric scaffolding.Parts are not fragments of wholes, but simply parts.' 18 Allen's understanding of 'field' went beyond hypostyle mosques and other gridded spaces -'All grids are fields, but not all fields are grids.' 19and included examples from the field of art, music, and biology.However, through the characterisation of fields as, using his words, open-ended, anti-hierarchical, undifferentiated, expandable, and a bottom-up phenomena with a highly fluid shape and extent, he established a counter-model that undermines the classical architectural object.We will build on Allen's theorisation and on the religious and aesthetic requirements of Islam to put forward an alternative canonthe ideal Islamic templethat opposes Alberti's (Table 1), and will explain why hypostyle mosques comply with said archetype better than any other architectural type.

A de-centred temple
In Christian churches, the altar is the place of the theophany (that is to say, where God becomes tangible through the Eucharist), and the undisputed focal point of a liturgy that revolves around it.To stress its sacred character and central role, it is often raised and framed by associated elements (such as iconostasis, altarpieces, and ciboria).Due to this, all Christian churches are, by definition, highly centred buildings and their space is usually hierarchical, sequential, processional, and highly readable.
In the case of Islam, the focal point of worship is the Kaʿba ( ‫ﭐ‬ ‫ﻟ‬ ْ ‫ﻜ‬ َ ‫ْﻌ‬ ‫ﺒ‬ َ ‫ﺔ‬ , lit.'the Cube') in Mecca, towards which Muslims around the world direct their prayers. 20In mosques, worshippers form parallel rows in front of the wall that faces Mecca, that is called qiblah ( ‫ﻗ‬ ‫ﺒِ‬ ‫ﻠْ‬ َ ‫ﺔ‬ , lit.'direction') and is signalled by a small niche, the mih ̣ rāb ( ‫ﻣ‬ ‫ﺤ‬ ‫ﺮ‬ ‫ﺍ‬ ‫ﺏ‬ ).While the s ̣alāt ( ‫ﺻ‬ َ ‫ﻼ‬ َ ‫ﺓ‬ , 'prayer') is directed by the imām ( ‫ﺇ‬ ‫ﻣ‬ ‫ﺎ‬ ‫ﻡ‬ ) and therefore its pulpit, the minbar ( ‫ﻣ‬ ‫ﻨ‬ ‫ﺒ‬ ‫ﺮ‬ ), as well as other elements such as the mih ̣ rāb or the maqs ̣ūrah ( ‫ﻣ‬ ‫ﻘ‬ ‫ﺼ‬ ‫ﻮ‬ ‫ﺭ‬ ‫ﺓ‬ , lit.'closed-off space'), can act liturgically and symbolically as local centres; they do not compete with the universal centrality of the Kaʿba and, unlike the Christian altar, do not have an overarching spatial effect nor are able to generate a clearly centralised architectural form.In the words of James Dickie: One definition of a mosque could be a building erected over and invisible axis, an axis which is none the less the principal determinant of its design.The Muslim world is spread out like a gigantic wheel with Mecca as the hub, with the lines drawn from all the mosques in the world forming the spokes. 21erefore, and independently of their morphology, all mosques are, at least conceptually, directional and de-centred spaces or, rather, spaces whose ritual and symbolical centre lays outside of them and, in most cases, very far away.Significantly, the only exception to this rule is the Masjid al-Haram, the mosque built around the Kaʿba in Mecca.This is 'the only non-directional reli-gious building in the Muslim world' and the only mosque where worshipers assume a radial concentric pattern when praying (Fig. 5). 22In all other mosques, the lack of an internal centre implies a type of space that, at least ideally, is homogenous and anti-hierarchical, especially if compared with Christian churches.
The 'formless' nature of Muslim liturgy or, rather, the lack of a Muslim liturgy in the Christian sense, and the fact that the direction of worship can be easily indicated by the mere addition of a niche, implies that almost any space can be used as a prayer hall, since its shape and spatial configuration are somehow irrelevant.In fact, following Muslim expansion outside the Arabian Peninsula, many buildings could be easily turned into mosques with minor alterations and different types of mosques were developed, including partially or fully centralised ones, such as the Iwan mosques, developed from the Sasanian-Persian domed architecture, or the Ottoman examples modelled on Hagia Sophia, the epitome of Byzantine architecture.Yet, while the lack of strict formal requirements allowed for a building as centralised and hierarchical as Hagia Sofia to be turned into a mosque, it could be argued that centralised buildings contradict the very essence of an Islamic worship centred on its axis mundi at Mecca.On the contrary, the hypostyle mosque (a rectangular hall with parallel rows of columns, usually accessed from an adjoining courtyard) is the most literal architectural rendering of a worship whose traits it mimics since both are decentred, homogenous, and anti-hierarchical; the most economic response to the lack of any formal or spatial requirements beyond housing parallel rows of worshippers.In other words, the type can be seen as the bare minimum architectural response to the bare minimum requirements of Islamic rituals and, hence, as its most precise and direct spatial translation.In many cases including Córdoba, the arcades were perpendicular to the qiblah, enhancing its visibility from the entrance courtyard and creating parallel aisles that, conceptually, would converge in the distant Kaʿba.
According to Moneo, translating Muslim worship into architecture: […] involved leaving behind the unity and singularity that characterised traditional Western architecture and the appearance of a generic and non-particularised architecture […] the axiality and sequentiality, as well as the imposing centrality of the first Christian basilicas, disappeared in the mosque for the sake of a neutral and not-characterised space.The focus of the Christian space, the altar, was absorbed by the whole. 23

Anti-hierarchical and homogenous
Christianity relies on a highly hierarchic, heterogenous, and articulated structure of mediators between humanity and God that includes the Virgin Mary, the apologists and apostolic church fathers, the four evangelists, the twelve apostles, angels, saints, and the complex ranks of the church and the monastic orders, etc.This tendency towards mediation can be traced back to the Bible, a collection of texts by different authors narrating the creation of the World, the history and religion of the Israelites (Old Testament), and the life, death, and resurrection of Jesus (New Testament).The fact that the four gospels of the latter are called 'according to' the four evangelists stresses the fact that the Bible is a human creation that conveys the word of God in a mediated and hermeneutic way.Ultimately, the very figure of Jesus Christ, that is to say, of the human incarnation of God sent to Earth to live among us, can be seen as the supreme mediation between God and humanity.
In fact, it could be argued that Christian art has traditionally been more concerned with representing these heavenly and earthly mediators rather than divinity itself.Raphael's Disputation of the Holy Sacrament, (1510) or El Greco's The Burial of the Count of Orgaz (1586) (Fig. 6) are two beautiful examples among many others of how Christian iconography rendered the complex and multi-layered hierarchy of figures that, somehow, fill the void between Heaven and Earth, God and humanity.There is a clear correspondence between Christian cosmology and most Christian churches (both with centralised and cross plans) since both are vertical structures assembled from heterogenous parts following hierarchic rules.
On the contrary, while Islam considered itself a continuation of the Abrahamic religions and incorporated key Jewish and Cristian figures to its own tradition (such as the 'prophets' Adam, Noah, Abraham, Moses, Jesus, or the Virgin Mary and the angels) 24 their previous mediating role was radically terminated by the Qur'an, which is understood as the final revelation.In fact, and this is crucial to understand the differences with Christianity, the Qur'an is not an account or an interpretation by a human actor, but the direct and ultimate word of God to humanity, dictated by the Archangel Gabriel to Muhammad, the final prophet, who transcribed it in a verbatim way.The idea that the Qur'an brings a definitive closure to the previous chain of revelation is clearly conveyed by the expression 'Seal of the Prophets', referred to Muhammad.This made translating it unacceptable since any translation implies a loss of precision: 'The Qur'an was revealed in Arabic which makes its literary style part of the same revealed action […] The Qur'an is the Word of God in an absolute way.' 25 Beyond the final nature of its revelation, Islam is based on the absolute submission (Islam means 'submission' and Muslim 'one who submits') towards a God that is defined by its radical separation from humanity, an alterity that makes any mediation inconceivable.Juan Aranzadi, building on Claude Lévi-Strauss' Tristes Tropiques (1955), argues that said common submission, It is not, therefore, a community in the sense of an organic whole defined by internal ties between its parts, but a mass obtained by simple aggregation or addition.[…] A 'community' defined by a vertical relationship with an unrepresentable and ungraspable God (both dramatically and plastically) and a horizontal accumulation of individuals […]. 26nce it is defined by individual relationships with God that are identical, the ummah is, conceptually, egalitarian, homogenous, and horizontal.In spatial terms, it can be seen as an isotropic mass or, even, as a shapeless fluid lacking internal structures or articulations.Likewise, the hypostyle mosque is shaped by the mere repetition of identical elements, has horizontal proportions and, as we will see especially in the Mosque of Córdoba, is also conceptually shapeless.Precisely due to this, hypostyle spaces have been often used through history to contain elements that are isotropic and shapeless, as happens with water cisterns.Hence, there is a clear correspondence between the character of the ummah and that of hypostyle mosques, which does not mean that all of them were perfectly antihierarchical, homogeneous, and horizontal.In fact, there were significant differences even among its earlier examples in Iraq and Syria.While the Great Mosque of Kufa (637) (Fig. 7a) was relentlessly homogenous and showed a total lack of spatial hierarchy, the Great Mosque of Damascus (706) (Fig. 7b) is organised around a much wider central nave surmounted by a dome, and its plan still shows a strong axiality and hierarchy reminiscent of Roman basilicas. 27

Nuanced homogeneity
The mosque of Córdoba is somehow in between these two examples.Its first three stages still show some of the axiality and hierarchy of earlier Umayyad temples, such as the Great Mosque of Damascus and the al-Aqsa Mosque in Jerusalem, albeit in a very weakened way.In fact, even if the eleven aisles of this area have the same height, and therefore we cannot speak in terms of proper naves, the central one is slightly wider, while the outermost ones are slightly narrower (Fig. 10). 28The change is small enough for these spaces not to be perceived as clearly different, but big enough to create a subtle hierarchy and symmetry along the central axis leading to the mih ̣ rāb.Furthermore, the distribution of spoliated Roman or Visigothic capitals and Islamic copies also followed a symmetric pattern along said axis and, in the al-Hakam II extension, the grey and pink column shafts created symmetric diagonal lines directed towards the mih ̣ rāb. 29he system also permitted the creation of visual emphasis and local centres in this area.While the aisles were originally covered by flat wooden ceilings, said uniformity was broken by four impressive crossed-arch domes: one over the entrance to the extension, in the so-called Villaviciosa Chapel, and three over the maqs ̣ūrah, the area immediately in front of the mih ̣ rāb reserved for the caliph and his entourage (Fig. 8). 30These spaces were further marked off from the rest of the mosque by an elaborate screen of intersecting polylobed arches and a much richer decoration including, in the central dome in front of the mih ̣ rāb, the same golden mosaics made by byzantine craftsmen that decorate the qiblah.In plan, these four domes draw a 'T' along the central aisle and punctuate the hall by bringing in natural light into a space that was originally lit by oil lamp chandeliers and, therefore, quite dark.All these strategies were aimed at stressing the direction towards the qiblah and enhanced the visibility of the mih ̣ rāb.Yet, the subtle symmetry and axiality of the space were later weakened by the Al-Mans ̣ūr sideways extension, which was fully uniform.
The maqs ̣ūrah was originally intended to protect the ruler from assassination. 31 In fact, in Córdoba, it was originally separated by a wooden lattice and accessed from an independent entrance in the qiblah.However, its lighting, formal complexity, and enhanced decoration set it visually apart from the rest of the space and the congregation thus becoming a symbol of power.According to Bloom and Blair, Córdoba's maqs ̣ūrah 'seems to have emphasized the great pomp and ceremony with which the Umayyad caliph surrounded himself'. 32Heba Mostafa has studied the tensions between the congregation's open access to the rulers and the tendency of the latter towards autocratic rule and separation. 33According to her, during the early stages of Islam, mosques became increasingly politicised, a process that informed the two elements that were reserved for the caliph or his governors, the minbar and the maqs ̣ūrah, turning them into instruments and a 'metonym of authority'. 34More in general, the politicisation of mosques may have moved them away from their original simplicity: These shifts represented a specific brand of Umayyad Arabo-Islamic authority, increasingly self-aware and evoking clear royal associations that served Islamic functions.The austerity of the Mosque of the Prophet in Medina thus eventually gave way to a space charged with and representative of the nature of the emerging caliphate and the contested authority of Islam's early rulers. 35nce, in Córdoba, the general homogeneity of the whole was challenged not only to stress the directional nature of the space, but also to express the social hierarchy and the political power, somehow betraying the ideal egalitarianism of the ummah.

Syncretism and paradoxical repetition
Early Islamic art and architecture had a strong syncretic character and was able to successfully incorporate, re-combine and re-elaborate the previous artistic and constructive traditions of the territories where the new civilisation expanded.The origin of hypostyle mosques has been traced back to the House and Mosque of the Prophet in Medina, 36  Córdoba is a good illustration of Islamic syncretism as well as of original constructive ingenuity: its double tiered arches follow the example of Damascus and have also been related to the Roman Acueducto de los Milagros in Merida 'but to allow the lower arches to span freely through the open space without any masonry to fill the interstices was an innovation'. 37Its horseshoes arches were common in Visigothic architecture in the Iberian Peninsula, the alternating coloured voussoir can be found in Umayyad building such as the Dome of the Rock in Jerusalem, its ribbed domes have been related with Armenian and Sasanian architecture, and its glass mosaics were done by Byzantine craftsmen.
But, beyond the recycling of previous types and constructive elements, the builders of the Mosque physically recycled a great amount of spolia taken from nearby buildings and ruins.In fact, the most accepted explanation for the unusual double arcades is the availability of relatively small Roman and Visigothic columns, which were abundantly reused in the original mosque.The use of disparate components required a degree of flexibility and created all sorts of combinations.For example, there are columns with and without base to adjust their height, shafts of different colours and materials and all kinds of capitals of different styles and quality.In the later expansions, the recovered elements were gradually substituted by new and standardised shafts and capitals that were beautifully stylised (and hence Islamised) copies of Corinthian ones.Also, while originally the alternating voussoirs were made up of exposed yellow stone and red brick, in the al-Mans ̣ūr extension the masons did 'cheat in details; for instance, in order to give the effect of two colours, they used not brick and stone but painted plaster'. 38herefore, while the Mosque is obviously an architectural system based on repetition, said repetition is paradoxical.On the one hand, it is radical and relentless since the general shape, dimensions, and proportions of the 'type arcade' were kept identical from the original building to its last expansion.On the other hand, the specific components with which the system was assembled show a great variability, especially in the earlier stages, that are a masterpiece of 'adhocism'.The difference between the consistency and identity of the 'macro' and the 'micro' creates an ambiguous feeling where different areas of the Mosque look very similar and, yet, somehow different.

Open and unstable
As we have seen, Alberti's ideal temple was a closed and stable object and it was considered a rendering of Platonic ideas that were, by definition, perfect and eternal.More broadly, his understanding of architecture was marked by an aspiration to permanence that has been a key component of Western architecture since classic antiquity.
Things are different in Islamic art due to a spirituality that is strained between an absolute divinity, that is all-mighty, ubiquitous, and eternal, and the insignificant, located, and transient nature of all earthly things: 'And you see the mountains, thinking they are solid, and yet they will pass away like the clouds,' says the Qur'an (27:88).Consequently, Islamic architecture is marked by the understanding that all human creations are fundamentally imperfect and temporary: 'it comes as close as building can to project the Muslim view that God is continuously creating and re-creating the world and that material things have thus a fugitive and ephemereal [sic] existence'. 39ypostyle halls are, due to their strictly additive and quantitative logic, a typology without scale.As such, they could be used for the two main types of mosques: the smaller ones for daily prayers by small groups that were operated privately, like the Mosque of Cristo de la Luz in Toledo with its 3 × 3 bays and 8 × 8 m plan, and 'congregational mosques', also called 'great mosques', for the Friday worship of a wider community, that were built and controlled by the rulers, like the vast Great Mosque of Samarra measuring 240 × 156 metres (Fig. 9). 40urthermore, their inherently adaptable character embodied like no other type the Islamic embracing of transience and made them particularly suited for the expansions required by a growing urban population during the first centuries of Islam.Perhaps more surprisingly, it also allowed to shrink previous structures when needed, as happened with the tenth-century reconstruction of the Sfax Mosque. 41Another interesting example of impermanence are the Kutubiyya Mosques in Marrakesh; in this not fully understood case, the original mosque was abandoned and left to ruin after a new one, that was an almost identical copy of the original, was built adjoining its qiblah wall with only a slight change of orientation.In short, while the canonical architectural object is closed and stable, and would be spoiled by even a small addition or subtraction, hypostyle mosques are open and unstable, and can sustain big transformations keeping their consistency and identity.
The Mosque of Córdoba epitomises this capacity (Fig. 10).As is well known, after its initial construction by ʿAbd al-Rah ̣ mān I (785-787) the Mosque hall was  The mosque's capacity to be expanded and changed while maintaining its distinct identity explains why it has attracted more critical attention than other hypostyle mosques.This is in fact a key component in Allen's theorisation of fields and the main driver of Moneo's analysis: The Mosque of Córdoba is perhaps an exceptional example: its traits, its formal mechanisms of composition, are so firm that, once they were defined, they fixed both the image and the structure of the building forever, without either of them being substantially altered by the interventions that took place over the years. 42ile the building is less homogenous that other hypostyle mosques (such as the great mosques of Kufa or Samarra), its unparalleled transformations make it a better example of our hypothetical canon.However, it needs to be noted that these aspects are closely interrelated since the traces of its expansions, especially the remains of former outer walls that divide the hall into perceivable sectors, clearly weaken the homogeneity of the whole (Fig. 11a).If the mosque had been built originally with its final size and shape, a hypothesis that we have rendered (Fig. 11b), the outcome would obviously have been much more homogenous, but it would have not expressed Islamic embracing of openness and shapelessness in the same way.

Shapelessness and irrelevant limits
If we focus on the Mosque's transformations under Islamic rule, the way in which they were carried out is as meaningful as the expansions themselves.While the first two were done towards the south, demolishing and rebuilding the qiblah twice, the last one was done laterally, towards the east, keeping the existing qiblah and mih ̣ rāb, due to the steep topography of the Guadalquivir riverbank that prevented further expansions towards the south.These changes, aimed at increasing the occupancy in the most simple and economic way at each moment, show a deep disregard for the shape of the building.In fact, the proportions of the prayer hall changed from (roughly) 2 × 1 in the original mosque to the opposite (1 × 2) after the third extension and, finally, almost 1 × 1 after the al-Mans ̣ūr expansion.This lack of consideration towards architectural form is clearly opposed to Alberti's canon that is based on strictly formal consideration on the shape and proportions of the building.Form is not only closed and stable but also carefully determined and specific, and that is precisely what allows to convey a given symbolical meaning.It could be argued that, for Alberti, architectural form is not only the main attribute of architecture, but architecture itself.On the contrary, the main preoccupations of the builders of Córdoba were purely functional and form was the outcome of changing requirements and local conditions.As such, the shape of the building is contingent, generic, meaningless, and, to a great extent, irrelevant.
Due to this, the Mosque has been often described using the metaphor of the 'forest of columns', that is to say, of an intricate space defined by a repetition of similar elements the boundaries and shape of which are changeable and entirely inconsequential.This sense of indetermination and shapelessness is stressed by the fact that the arches facing the courtyard were left open for many centuries, hence blurring the limit between inside and outside: [The] hall of pillars would resemble a broad grove of palm trees and provide everchanging views into the interior of the columned hall.Formerly this "grove" was much lighter.Today the arches facing the courtyard are all walled in with the exception of two gates. 43e limits of the mosque are analogous to those of the arabesque, they can trim the gridded pattern in any direction and at any point without undermining its integrity and internal logic, and they can be tangible and material or intangible and virtual.This is very different to what happens with Christian churches, wherein the limits and outer shape have an essential symbolical and representative role and usually reflect their interior organisation and spaces.

A concave and introverted space
However, the fact that the boundaries of hypostyle mosques are irrelevant and can be changed as many times as needed, does not mean that the function of demarcation they perform is equally unimportant.On the contrary, the need to separate the interior from the exterior was key in Islamic poetics and 'was rooted in the need to carve out oases of order and coherence out of a world which was perceived as being perilous and chaotic, and to wall them in to protect them, creating the temenoi of Hellenistic cultures', 44 something that was reinforced by the cult of ritual ablutions and the pure-impure separation.Unlike in Christian temples, the emphasis in creating protected, clean, and introverted environments implied a generalised disregard for the outer appearance of buildings: […] whereby even a monumental structure, such as a congregational mosque, is completely hidden by being totally surrounded by secondary adjacent buildings (for instance a bazaar).This 'hiding' of major monuments goes hand in hand with a total lack of exterior indications of the shape, size, function or meaning of a building.[…] In other words, rarely does a facade give any indication of the inner organization or purpose of the building in question, and it is rare that an Islamic building can be understood, or even its principal features identified, by its exterior. 45e Mosque of Córdoba is a good illustration of this quote: its outer walls have few and small windows and are a seemingly random patchwork of large blank surfaces, heavily decorated gates, buttresses, and, in the south façade, deep structural arches (Fig. 12).Their heterogeneity reflects both the changes through time and the lack of any will to impose unifying and overarching compositional principles upon them.In fact, it is difficult to describe them as façades in the Western sense of the word, that is to say, as an orderly membrane mediating between inside and outside, the appearance of which is key for the image and identity of the building.Even the rhythm of the buttresses, that are, arguably, the most unifying element in the west, north, and east walls, is not entirely regular, and long sectors of the courtyard walls are devoid of them.Furthermore, the surrounding urban tissue made up of narrow streets, does not allow to have a general view or grasp the real size of the building from the outside.Confirming Norberg-Schulz's opinion that 'Islamic architecture is "introverted", and its meaning becomes manifest primarily in enclosed gardens, courtyards and interiors', 46 the outdoor space that allows a better and more general understanding of the Córdoba Mosque is its courtyard.This space is not only much bigger than the surrounding streets, but one of the biggest outdoor spaces in central Córdoba, even today (Fig. 13). 47The concave nature of the Mosque is also clear in the contrast between the ornated and rich interiors and the predominantly blank and rough outer walls, which reflects an overarching principle of Islamic aesthetics, that of the 'hidden beauty': 'If God is beautiful and loves Beauty and if this God has chosen to be hidden, then his servants must prefer beauty that is veiled.' 48meaningless building?
As we have seen, Christianity relies heavily on visual figuration to represent the divinity and its associated figures and symbols.A clear example of this is the iconographic overload of Gothic cathedrals whose many sculptures, stained glass windows, and other added elements, such as paintings and altarpieces, depicted all sorts of religious characters and passages of the Bible, as well as secular images and everyday life scenes.Furthermore, the Greek or Latin cross plans of most Christian temples also carry meaning inasmuch they are stylised figural representations (icons) of the body of Christ in the cross (Fig. 14).As we have seen, the shape of the Albertian temple was also meant to convey religious meaning, albeit in a different way; while a Gothic cathedral did so in an analogic and figurative way through its very shape, the Renaissance church did so in a more sophisticated and Neoplatonic way, through a perfect geometry that mirrors the perfection of god's creation.This change in the mode of representation, however, did not preclude the presence of iconographic content; in fact, Alberti mentioned frescoes, pictures and statues.
Contrary to the widespread belief, there is no explicit prohibition of figurative representations of living creatures in the Qur'an and, in fact, there are many instances of images of animals and human beings in Islamic secular art. 49owever, in the realm of religious art and architecture, there was a strict aniconism which derived from the radical rejection of idolatry, some h ̣adı ̄ṯ h ( ‫ح‬ ‫د‬ ‫ي‬ ‫ث‬ , sayings attributed to the prophet) that seemed to condemn images, and the belief that 'in fashioning the form of a being that has life, the painter is usurping the creative function of the Creator and thus is attempting to assimilate himself to God'. 50eyond this, representing Allah Himself is not only unthinkable but, perhaps more importantly, impossible: unlike nature, that is corporeal, ephemeral, and finite, He is incorporeal, eternal, infinite, and, therefore, unrepresentable.Moreover, unlike the Christian God that 'became flesh' through His embodiment in Jesus Christ, hence acquiring a representable image, Allah decided to stay hidden and to manifest Himself only through His word.
Therefore, even if mosques are usually heavily decorated, they are devoid of any religious iconography and their form is not meant to represent divinity in any figural way.Due to their generic, neutral, and abstract character, hypostyle halls are particularly inexpressive and blank, a sort of 'zero degree' architecture.Once again, Córdoba is a clear illustration of this since it is not possible to attach any meaning to a contingent and changing shape.
However, its meaningless shape and the lack of religious iconography do not imply that the building did not convey any meaning.In fact, a key component of the decoration of most mosques is Arab calligraphy, arguably the highest expression of Islamic art due to the sacred character of Arabic, the language chosen by Allah to deliver His last revelation.The epigraphic content in mosques usually includes Qur'anic verses, historical accounts, and data about the building foundations and patrons.While Christian cathedrals have been metaphorically described as 'books of stone', but they relied mainly on images since the population was overwhelmingly illiterate, Mosques were even more so, since the many texts that covered them were aimed at a population with relatively high literacy rates.
The epigraphic content of the Mosque of Córdoba is particularly rich in the al-Hakam II extension, the area that is more complex and heavily decorated (Fig. 15). 51The Kufic inscriptions include both historical accounts and carefully selected Qur'anic verses that, according to Nuha N. N. Khoury, conveyed a clear political message meant to legitimise the Umayyad dynasty.This was done through 'a subtle weaving of historical, cultural, and mythical paradigms […]  this charge aligned the mosque's dynastic identity with its new caliphal one by rewriting the past from the vantage point of the present'. 52The epigraphic programme links the mosque with the Umayyad caliphal past in Syria, presents the re-establishment of the second caliphate in Córdoba as the fulfilment of a series of prophecies, and describes the new building as an image of the 'first house of worship' (the Prophet's Mosque at Medina).Khoury states, 'This ideological construction aligned the Umayyads with the original source of caliphal authority and represented them as the true caliphs of the Umayyad-Abbasid-Fatimid triumvirate.' 53ccording to Khoury, the description of the Prophet's Mosque in Medina from the Al-ʿIqd al-Farı ̄d (attributed to ʿAbd Rabbih, ʿAbd al-Rah ̣ mān III's court poet) contained discrepancies with the building that seemed aimed at stressing its similarities with the Córdoba Mosque: 'These correspondences and inconsistencies indicate that the description was a critical instrument of iconographic transfer that conflated two monuments in order to re-create one as an image of the other.' 54 Beyond the political dimension of this symbolical appropriation, these inscriptions established a genealogy that linked Umayyad mosques, singularly Córdoba and Damascus, with the source of Islamic legitimacy, the Prophet, through his 'first house of worship' in Medina.By doing so the Umayyad rulers consciously asserted the hypostyle type as the original and perfect Islamic temple.

Ungraspable endlessness
As we have seen, the lack of representations of Allah is not only due to a religious prohibition, but to the impossibility to do so.Allah is marked by His absolute incomparability (Tanzih, ‫ﺗ‬ ‫ﻨ‬ ‫ﺰ‬ ‫ﻳ‬ ‫ﻪ‬ ), He is not only incorporeal but also eternal, omnipresent, omniscient, all-mighty, and all-merciful; in other words, He is infinite in all His attributes, and infinity is, by definition, ungraspable and unrepresentable, a fundamental impossibility that marks Islamic spirituality and aesthetics.Muslim faith (ı ̄mān, ‫ﺇ‬ ِ ‫ﻳ‬ ‫ﻤ‬ َ ‫ﺎ‬ ‫ﻥ‬ ) is a heartfelt and intellectual certainty that does not rely on sensorial perception or tangible miracles. 55However, while Muslims can only know Him through the words He spoke about Himself and His creation, they may: … tolerate an occasional symbolism or comparability (Tashbih) between an attribute of His and that of His creation […] Islamic creativity thrives on the incipient consciousness of "gap" between Tanzih and Tashbih and the desire to bridge this.There is the transcendence (Dhat) and incomparability (Tanzih) of God on one hand and His attributes (Asma and Sifat), similitudes, allegorical constructs (Tashbih, Tamthil) and manifest signs (Ayat) on the other. 56presenting Allah's un-representability became the main challenge for Islamic aesthetics and, managing to do so, its biggest success.This seemingly impossible task was achieved by creating associations with its defining and most inexpressible trait: infinity.That is why Islamic art abounds in elements that seem to have no beginning and no end, no centre and no periphery, like music with a repetitive cadence or decorative patterns that suggest an extension ad infinitum: 'In making visible only part of a pattern that exists in its complete form only in infinity, the Islamic artist relates the static, limited, seemingly definite object to infinity itself.' 57 According to Norberg-Schulz: 'Islamic space is infinite rather than goal-oriented, although it is directed on the Kaʿba.' 58 The allusions to infinity were also meant to stress, by contrast, the transience and worthlessness of human experience.
Hypostyle mosques' potential endlessness is an obvious expression of said 'love of infinity'.In the case of the Mosque of Córdoba, there are other traits that recall infinity, in fact, at a conceptual level, the building has no shape, no boundary, no exterior, and no centre or, rather, has its centre everywhere.The well-known definition 'God is an infinite sphere whose centre is everywhere and whose circumference is nowhere', 59 despite predating Islam, captures its conception of divinity and how it informed Islamic art remarkably well.As we have seen, in Córdoba, there is no clear or overarching centre, but rather a series of elements that may act, whether spatially or ritually, as local ones (the crossed-arch domes, the minbar, and the mih ̣ rāb).This could be seen as a spatial rendering of an unrepresentable endlessness the centre of which is, like Allah, everywhere and nowhere at the same time.Hence, the Mosque, through its allegorical allusion to infinity, does not represent Allah, but rather His un-representability.

Immateriality and dissolution
We have seen how the Islamic belief on the transient nature of everything earthly implied an open and unstable view of architectural form.It also influenced architectural and artistic expression by imparting it with a visual feeling of immateriality that, according to Ernst J. Grube, had no real parallel in the history of art.This was often achieved by using ornamental patterns 'to disguise and "dissolve" the matter, whether it be monumental architecture or a small metal box'.In the field of architecture: Solid walls are disguised behind plaster and tile decoration, vaults and arches are covered with floral and epigraphic ornament that dissolve their structural strength and function, and domes are filled with radiating designs of infinite patterns, bursting suns, or fantastic floating canopies of a multitude of mukkarnas, that banish the solidity of stone and masonry and give them a peculiarly ephemeral quality […]. 60reover, the way in which intricate shapes and decorative patterns seem to dissolve the difference between line and surface, and surface and volume, together with the emergence of similar patterns and shapes at different scales, has brought many authors to suggest an 'intuitive fractal geometry' which seems a suitable conceptual model since it has often been associated with delicate or ephemeral elements, such as snowflakes, fern leaves, or capillaries. 61n Córdoba, and beyond the magnificent decoration of the qiblah and the maqs ̣ūrah area, this leaning towards material dissolution can be seen in elements such as the crenelated upper edge of the outer walls that dissolve the limit with the sky, the intersecting arches that shape virtual and 'dissolved' domes, and the poly-lobed and interlacing arches that formally dissolve the standard arcades.Perhaps more importantly, its archetypical double-tiered arcade also expressed a leaning towards dematerialisation through the generous gaps between the lower horseshoe arches and the upper semi-circular ones, which make the ensemble look much lighter, and through the visual effect of their red and yellow voussoirs.These idiosyncratic elements have a double and somehow paradoxical effect due to their chromatic contrast: on the one hand, they make the arches more visible while, on the other, they visually dissolve them by breaking their silhouette and merging them with other arches in front and behind.In that sense, they are similar to dazzle camouflages (Fig. 16) that were not aimed at making the ships they covered less conspicuous, but rather at hindering the perception of their true shape and size, or to the striped zebra coats, probably aimed at confusing predators.This highly visible pattern, together with the generous openings on the arcades that allow to see several of them at the same time, create visual interlacement between planes that are activated by the spectator's movements.The building is thus perceived as an everchanging and de-materialised lattice.
The uncommon structural organisation of the arcades also aimed at making the building look as light and ethereal as possible; in a seemingly counterintuitive way, the upper arches are significantly wider than the lower ones, and both are thicker than the remarkably thin shafts of the columns, as if the Islamic builders wanted to defy the laws of gravity and common sense. 62These dimensional changes in the structural cross section required bespoke elements, the cymatium and modillion, to solve the transition between the capitals and the wider elements which rest on them.Felix Arnold conducted a detailed geometric analysis of Islamic arcades in Al-Andalus and explained why they are different to previous ones.Analysing the ratio between bay width and column width, he concludes: [The] thickness of the supports needed to carry an arcade was eventually cut in half compared to the Roman period.The aim of the architects at Córdoba appears to have been to reduce the physical impact of the arcade on the ground. 63ile he provides a strictly practical explanation for the 'thinning' of the lowest part of the arcades (to improve the visibility and increase the floor surface), it is obvious that this also significantly impacted in the general perceptual de-materialisation of the building.The anti-tectonic approach seems particularly noteworthy because it was applied, precisely, to the key load-bearing element: the arches and the column.

An emotional arabesque
We have already pointed out some similarities between the Mosque of Córdoba and the arabesque, the Islamic decoration par excellence based on the relentless repetition of interlacing geometric figures (Fig. 17).Both the arabesque and the Mosque are potentially endless fields that, conceptually, have no boundaries and no shape and whose effective boundaries and shapes are irrelevant.Both have no defined size and are inherently expandable; they lack a general centre and have, instead, a multitude of local centres.They are (overall) homogenous and anti-hierarchical, and they convey no specific visual meaning beyond a loose and allegorical allusion to an unrepresentable deity.Furthermore, the typical interlacing of arabesque that creates a virtual depth is replicated in the Mosque of Córdoba by the interlacing polylobed arches (Fig. 18) in the maqs ̣ūrah and, more importantly, by the visual interweaving between its permeable double arcades.While we have so far referred to the Mosque as a 'system' to stress its differences with the canonical architectural object, perhaps it could be more precisely described as a three-dimensional or 'built' arabesque that, although more complex than decorative flat ones, follows the same compositional principles, conveys the same poetics, and triggers comparable aesthetic emotions.In fact, the effect that the Mosque has on us is very similar to that of arabesques, as evidenced in this quote by Jo Tonna: [The] repetitive rhythms of Arab-Islamic architecture assume the cathartic properties of ritual prayer, calming the mind and directing it to introspection and communion with the Absolute. 64ich is remarkably similar to this one by Sufi mystic Titus Burckhardt: [The] arabesque, with its rhythmic repetition serves quite a different artistic purpose than does pictorial art.It is a direct contrast to it, as it does not seek to capture the eye to lead it into an imagined world, but, on the contrary, liberates it from all preoccupations of the mind, rather like the view of flowing water, fields waving in the wind, falling snow or rising flames.It does not transmit any specific ideas, but a state of being, which is at once repose and inner rhythm. 65ese quotes suggest that Islamic architecture demands a mode of perception that is intuitive, kinesthetic, and somehow distracted, 66 as opposed to the intellectual, visual, and attentive observation usually associated with Western architecture.In the case of Córdoba, the building is experienced at its fullest if perceived in a dynamic way that enhances its repetitive character by wandering through it in the same way that our gaze roams the surface of an arabesque, without being anchored to anything in particular.It could be argued that the ensuing soothing and 'altered' state of being would be more intense that the one described by Burckhardt since, in this case, the beholder is 'inside the arabesque' and activates its visual interlacements and parallax effects by moving through its repetitive and seemingly endless arcades.
Hence, while the Western architectural object is usually meant to convey ideas by appealing to our rational mind, Islamic architecture does not convey any specific ideas and is aimed, instead, at triggering states of being and emotions, echoing the idea that believers can only 'see' a hidden God with their hearts. 67Furthermore, by creating seemingly dematerialised environments that reflected the temporary nature of every human creation, Islamic architecture inevitably mirrored our own passing nature, prompting the unavoidable lyrical agency of becoming.In doing so, it achieved a remarkable feat: to create contemplative and moving atmospheres that would allow us to feel God and marvel at the beauty of His creation and, at the same time, act as an emotional lookout upon ourselves.

Conclusion
We have seen how Islam established itself as a continuation of Judaism and Christianity.However, although it kept and adapted key elements of these faiths, it gave rise to a religion with decisive differences on the nature of God, His revelation, and our relationship with Him.Islamic architecture carried out a similar operation: on the one hand it arose from the appropriation of typologies and constructive elements of previous civilisations; on the other, it decisively recombined and transformed them to give rise to a new and unmistakably Islamic expression able to respond to the aesthetic requirements of a new civilisation.
In this paper, we have tried to distil and systematise the hypothetical features of the ideal mosque, putting forward a canon which, as far as we know, was never explicitly formulated by Islamic authors but can be inferred from Islamic theology and aesthetic principles.We have also seen how this ideal construction would be strikingly different and, in many of its key characteristics, opposed to the canonical architectural object outlined by Alberti during the Renaissance.We have posited the hypostyle mosque as the clearest and most literal typological expression of said archetype due to its decentred, anti-hierarchical, homogeneous, and repetitive character and its many analogies with infinity, which allowed to recall Allah's own endlessness, hence solving the gordian knot of representing an unrepresentable God.
We focused our analysis on The Mosque of Córdoba because its expansions and the capacity it has shown to withstand radical alterations make it a paradigmatic example, not only of Islam's embracing of transience and its open and unstable understanding of architectural form but also of the paradoxical 'strength' of this seemingly 'weak' approach.By mapping the Mosque against the ideal temple that has been tentatively outlined in this paper, we have seen that it does not fully comply with it.Other hypostyle mosques, in fact, were more homogeneous and anti-hierarchical, and the traces of its expansions do undermine the overall regularity of the space.We have also seen how the maqs ̣ūrah area, meant to protect the caliph, also acted as a visible symbol of his separation from, and power upon, the rest of the congregation and how the rich epigraphic programme was hijacked in favour of the political interests of the Umayyad rulers.These features undermined the equality of the members of the ummah, and showed a very human, and all but pious, ambition and vanity that defied the temporality and insignificance of human existence.But, beyond these earthly contingencies, the Mosque of Córdoba seems a remarkably accurate materialisation of the ideal Islamic temple and, arguably, a particularly beautiful one.
Finally, we have put forward the idea of 'built arabesque' as a conceptual model to describe the unique compositional trait of this space as well as the perceptual effects and aesthetic emotions it triggers.As we have said, it is precisely due to a nature that seems opposed to Western paradigms that the Mosque of Córdoba has attracted a significant critical attention from Western scholars and architects.But, beyond its character autre, these authors have also noted that several of its themes anticipated much later developments in Western art and architecture.For example, Allen mentions Le Corbusier's Venice Hospital, Renzo Piano's focus on an individual joint that often generates the whole, or Minimalist art, and many authors have noted how Islamic architecture prefigured the abstract and non-figurative nature of Modern architecture, although reached from very different standpoints.While it was not a primary aim of this paper, the themes we have explored may allow us to extend the list to the 'mat-buildings' theorised by Alison Smithson in 1974; concepts such as Oscar Hansen's 'Open Form' (1959), John Habraken's 'Open building' (1961),and Charles Jencks' 'Adhocism' (1972); the 'immateriality' and perceptual dissolution explored by contemporary Japanese architects such as SANAA, Jun Aoki, and Sou Fujimoto; the renewed interest in architectural informality; or current experiences on computational design that generate complex shapes that recall the intricate and fractal nature of Islamic architecture.
Facing an apparently impossible task, early Islamic builders were able to create immaterial, contemplative, and seemingly endless atmospheres.This innovative programme for the dissolution of architecture was already fully formulated in an initially small mosque built more than 1,200 years ago with the spolia of previous civilisations.There began a space that heralded a variety of contemporary practices with the potential to renew the discipline by undermining a canonical architectural object that still limits the Western understanding of the built environment.

Figure 1 .
Figure 1.Renaissance centralised plan church, The Delivery of the Keys to Saint Peter, 1481-1482, by Pietro Perugino, Wikimedia Commons, in the public domain

Figure 5 .
Figure 5.The undisputed centre of Islamic spirituality: the al-Kaʿba l-Mušarrafa in the Masjid al-Haram, Mecca, photo by Camera Eye, 20 October 2006, CC BY 2.0, Wikimedia Commons

Figure 6 .
Figure 6.The Burial of the Count of Orgaz, 1586, by El Greco, Wikimedia Commons, in the public domain

Figure 10 .
Figure 10.Stages of the Córdoba Mosque under Islamic rule: (from left to right) original mosque of ʿAbd al-Rah ̣ mān I (785-787), and expansions under ʿAbd al-Rah ̣ mān II (832-848); al-Hakam II (961); and al-Mans ̣ūr (987-988), drawn by the author, 2023 Figure 11.(a) Plan of the Mosque of Córdoba after its last Islamic expansion under al-Mans ̣ūr (987-988); (b) Hypothetical plan of the Mosque of Córdoba if it had been built at once with its final capacity, size, and shape, drawn by the author, 2023

Figure 14 .
Figure 14.Disegno di Tempio a Crociera, illustration in I Quattro Primi Libri di Architettura, by Pietro Cataneo,1554, in the public domain

Table 1 .
Comparison between the Western architectural object and the ideal Islamic temple although they may have been influenced by hypostyle structures from antiquity, like Persian apadanas