The Temple of Poseidon in Poros: The Temple of Poseidon is situated in the northern part of Poros. What remains today of this sanctuary are mere ruins. It used to be the center of the Kalaureian amphictyony that functioned as a voluntary co-operative for dealing with religious as well as civic issues for city-states including Epidauros, Prassies, Hermione, Aigina, Athens, and Orhomenos. It is believed to date back to the year 520 BC as claimed by N. Faraklas. I. Stamatiou states that it was built in the 6th century BC while some others claim that it was built even earlier than that.
The main temple structure is in Doric style architecture. However, some of its columns do reflect the Ionian style. The dimensions of the temple are 27.4 x 14.4m having 6 columns on its short side and 12 on the long side, following the Dorian Order.
Giannis Poulakis, in his book Poros and Its History, writes, "The Temple of Poseidon soon developed into a prestigious and Panhellenic place of worship and became a center where many Hellenic cities founded the first and most powerful in the Hellenic world amphictyony". Demosthenes, the ancient great orator, came to the temple of Poseidon's Temple demanding his right of sanctuary when he was being chased by Philip the King of Macedonia. He killed himself here by drinking the poison hemlock in 322 BC.
The temple of Poseidon once contained several statues but they have all been stolen over time. For example, the statue of Poseidon was estimated at 5 meters in height. All that now remains of it is the foot: a 70-centimeter long piece, which is housed at the Poros Museum.