Eleusis, by far the most respected sanctuary of Attica in ancient times, formed the background for the so-called Eleusinian Mysteries, the worship of the goddess Demeter and her daughter Kore. According to Eleusinian mythology, Demeter had searched for her lost daughter Kore at the well of Eleusis. This well was located just outside the wall of the sanctuary, which shielded the actual Holy Court from the outside world. Also outside the enclosure wall was a temple dedicated to Artemis Propylaea (“before the gate”) and a second temple dedicated to Poseidon, located on a spacious marble-clad square. Here the mystai gathered to undergo the cleansing rites which were mandatory before entering the sanctuary itself. Left and right, the entrance to the main square was “bordered” with two Roman triumphal gates, of which considerable remains have been preserved.
Access to the Holy Court itself was reserved for those initiated into the Mysteries, and passed through the Great Propylaea, a gateway with six enormous Doric columns (two of which are against the modern enclosure), adorned with a portrait bust of the Emperor Marcus Aurelius, who had the sanctuary redone after the havoc left by the marauding Germanic hordes of the Costobokes. The Great Propylaea are essentially a copy of the propylaea of the Acropolis in Athens.
The numerous renovations in the sanctuary are clearly visible on the map on the right (photo from museum).