Demeter's central cult was the Eleusinian Mysteries, celebrated for close to two thousand years at Eleusis near Athens and open to any Greek-speaker, free or enslaved, man or woman, who had not shed blood. Initiates underwent a night ritual in the Telesterion whose culminating vision was guarded by an oath of silence so well kept that, despite the Mysteries' enormous fame, no ancient writer plainly records what was shown; scholars reconstruct only fragments, and the debate over whether a sheaf of grain, a sacred drama of Persephone's return, or an altered state lay at the centre is unresolved. What the sources agree on is the promise: the initiate, unlike the uninitiated, could expect a better lot after death. The Homeric Hymn to Demeter preserves the myth the rite re-enacted, of the mother's search for her stolen daughter.
The Telesterion at Eleusis, the great roofed hall where the Mysteries' central rites were performed, was rebuilt and enlarged repeatedly across the centuries, most notably under the tyrant Peisistratus in the sixth century BCE and again in the fifth century BCE to a design associated with Ictinus, one of the architects of the Parthenon, each expansion accommodating the swelling numbers of initiates drawn from across the Greek and later the Roman world. The cult finally ended not by gradual neglect but by violence and decree: the Christian emperor Theodosius I's edicts of the early 390s CE banned pagan sacrifice across the empire, and in 396 CE the Visigothic king Alaric's forces sacked the sanctuary itself, bringing to a definitive close a rite that had run for close to two thousand years.