The Telesterion was a great hall and sanctuary in Eleusis, one of the primary centers of the Eleusinian Mysteries. The hall had a fifty-five yard square roof that could cover three-thousand people, but no one revealed what happened during these events beyond there being "something done, something said, and something shown". This building was built in the 7th century BCE and was an important site until it was destroyed in the 4th century CE. Devoted to Demeter and Persephone, these initiation ceremonies were the most sacred and ancient of all the religious rites celebrated in Greece.

Elefsina or Eleusis is a suburban city and municipality in Athens metropolitan area. It belongs to West Attica regional unit of Greece. It is located in the Thriasio Plain, at the northernmost end of the Saronic Gulf. North of Elefsina are Mandra and Magoula, while Aspropyrgos is to the northeast.