We first give an account of the discovery of the Antikythera treasure, which was found by Symian sponge divers in November 1900. Among other finds was the Antikythera mechanism, which is the ancient mechanism of the highest level of sophistication among the mechanisms that have been found until now and is considered as the highest technology mechanism in antiquity. We have included in our account information from recent literature. We also give a description of this mechanism and its function, use and purpose. Finally, we present some scientific arguments in favour of our suggestion that the creator of the Antikythera mechanism was Posidonius of Rhodes.