Eleusinion

thumb|upright=1.5|Remains of the Eleusinion, seen from the southeast. The platform at left is the northern end of the Temple of Triptolemus. The masonry wall in the background is the Post-Herulian Wall, which runs along the western boundary of the sanctuary. Eleusinion (), also called the City Eleusinion () was a sanctuary on the lower part of the north slope of the Acropolis in Athens, Greece, dedicated to Demeter and Kore (Persephone). It was the central hub of Eleusinian Mysteries within Athens and the starting point for the annual procession to Eleusis, in the northwest of Attica. Religious activity is attested in the area from the 7th century BC and construction took place throughout late Archaic, Classical, Hellenistic, and Roman periods. The sanctuary was enclosed within the new city walls built after the Herulian sack of Athens in AD 267 and it remained in use until the late fourth century AD.

Only the western part of the sanctuary has been excavated, which consists of an upper area and three terraces, centring on a small temple for the hero Triptolemus, an outer propylon (gateway) and a South Stoa. A circular building in the southernmost part of the sanctuary might be a banqueting hall dedicated to Plouton and a precinct at the northernmost edge of the area might have belonged to Hecate. Sculptural fragments have been discovered from an inner propylon which led to the actual Temple of Demeter and Kore in the unexcavated area to the east and literary sources mention further structures. Many inscriptions, sculptures, pottery vessels, and other offerings from the sanctuary have been recovered.