Eleusinion, Greek sanctuary in Ancient Agora of Athens, Greece

The Eleusinion is an ancient sanctuary in the Ancient Agora of Athens that features a rectangular temple structure with surrounding precinct walls. The remains show typical features of Greek religious architecture, including preserved foundations, column bases, and portico elements visible today.

Religious activity at the site is attested from the 7th century BC. A polygonal limestone peribolos wall was built around 575–550 BC, enclosing the upper terrace and its rocky outcrop. A temple was built around 490–480 BC, replacing the open-air walled sanctuary. In 350–325 BC a second entrance was cut into the south wall, and in the Hellenistic period the South Stoa and a western propylon replaced the old entrances. The sanctuary stayed in use until the late 4th century AD.

The name Eleusinion marks it as Athens' branch of the sanctuary at Eleusis: the sacred objects of the Mysteries were brought here before the festival and kept in the city for its first five days. After the Mysteries, the Athenian council met here to review how the rites had been conducted, including whether anyone had insulted the official in charge of purchases. The building probably also hosted the Thesmophoria, a women's festival for Demeter and Kore.

Only the western strip of the sanctuary, 18 to 40 metres wide, has been excavated; the eastern part lies beneath the houses of Plaka. The remains sit on the lower north slope of the Acropolis, south of the Agora, with the Panathenaic Way along the western edge. The ground is uneven grass and stone, so watch your footing.

Pausanias, visiting in the 2nd century AD, wrote that a dream forbade him from describing the inner sanctuary in detail, so he recorded only the temple of Triptolemus and the bronze bull standing before it. His silence marks the boundary between the outer court and the holier inner section holding the temple of Demeter and Kore.