The Eleusinian Mysteries (Greek: Ἐλευσίνια Μυστήρια) were initiation ceremonies hel every year for the cult of Demeter and Persephone based at Eleusis in ancient Greece. Of all the mysteries celebrated in ancient times, these were held to be the ones of greatest importance. These myths and mysteries, begun in the Mycenean period (c. 1700 BC) and lasting two thousand years, were a major festival during the Hellenic era, later spreading to Rome.