Sanctuary of Poseidon at Kalaureia, Ancient temple ruins in Kalaureia, Greece.

The Sanctuary of Poseidon at Kalaureia occupies the Palatia plateau at about 190 m on Poros. Its Doric peripteral temple, built around 520 BC, measured roughly 14.4 by 27.5 m with six columns on the short sides and twelve on the long ones, inside a peribolos wall enclosing some 53 by 26 m. Four stoas, a propylon of about 330 BC and Building I, a private complex with an andron, stand among the foundations.

Settlement began on the Palatia plateau around 1200 BC and was soon abandoned; a new community appeared from about 750 BC, and the first sanctuary arose at the end of the 8th century BC. Around 650 BC a first temple with an enclosing wall was built, together with the forerunner of the propylon, and the Kalaureia amphictyony was founded. The late Archaic temple and its peribolos followed around 520 BC; the sanctuary was sacked during the Third Mithridatic War and probably abandoned in the 2nd century AD.

The sanctuary displays remnants of ancient offerings left by seafarers and merchants, including terracotta figurines and carved stones bearing dedications. These objects show how ocean worship was deeply connected to the daily concerns of those who made their living from the sea.

The site is reachable via Poros island and accessed on foot through a walking path with moderate uphill sections. Sturdy footwear is recommended, and bringing water is advisable, especially during warmer months.

The site served as a refuge for the persecuted in ancient times, as the temple complex held special sanctuary rights that protected fugitives. This role made it a place of shelter for those fleeing danger.