It has been confirmed that the archaeological area round the sanctuary of Poseidon has been inhabited since the Prehistoric times, while probably the sanctuary existed since the Geometrical ones. All the tenements were completed in different time phases. Especially the building of the Sanctuary dates at the Archaic era - and does not seem to have sustained any changes afterwards. The formation of the sanctuary with a row of buildings, the oldest of which were built in 420 b.C. and the newest ones in 320 b.C., is dated at the Classic era. The relics of the town have reference to the Hellenistic era, whereas all seem to survive in Romaic one.

The Sancuary of Poseidon was built somewhere round 520 b.C. We do not know whether there was an older sanctuary. Its dimensions were 14,40 x 27.40 m. facing to the northwestern and it was doric, with 6 columns at the narrow and 12 at the long sides. It must have had internal colonnades, also doric. It was built by aeginian sinter.

The Sanctuary was found in a rectangular parvis, with dimensions 52,95 x 26,05 m. It had two entrances, one to the northeastern side, right opposite of the temple entrance, and a second one to the southeastern side, in the middle of the corresponding side of the sanctuary.

As far as the classic era is regarded, the only extra thing that we are aware of is the creation of a wider sacred precinct at the southeastern of the old one and an extention to the southwestern.

At the northwestern side of that extention, somewhere round 420 B.C., an archway was built, facing to the southeastern. Its dimensions were 9, 30 x 30, 20 m., probably 9 Doric pillars to the front and 4 Ionic at the central long pivot.

50 years later a new archway was built, to the southwestern of the previous archway, few relics of which were saved. Its dimensions were 30, 50 x 9, 45 m. and had 5 internal pillars.

20 years later opposite of it a new archway was built, facing to the northwestern side (dimensions 29, 65 x 7, 40 m.).

At the first Hellenistic years the constructive program of the sanctuary is continued and completed. Between the second and third archway a complex is built that contains the living quarters of the priests and at the southeastern a propylon Η shaped with archways to the front and back, with a total lenght of 13, 80 m and width of 6,90m.

About ten years after the propylon, somewhere around 320 B.C. a new archway was built (32, 80 x 3, 95 m.) at the extention of the third one, with Doric collonade.

It is one of the three biggest sanctuaries of Poseidon in Saronicos. The sanctuary shaped isosceles triangular with the sanctuaries of Afaia in Aegina and Poseidon of Sounio. It is found at the location Palatia, between Vigla and Prophet Helias.

The building construction at the southwestern side of the sanctuary (dimensions 31 Χ 11m.), might have been the Parliament of the town of Kalavreia. That was the meeting place for the delegates of the seven towns that participated in Amphictyony of Kalavreia. At the southwestern side of the Parliament there was a building (Demosthenis' monument or the Aesculapion).

The sanctuary was a famous shelter that accepted under its protection the hunted people. We know the name one of the implorers: Demosthenis. Demosthenis, the orator, was the most famous person who asked for shelter here, leaving Athens, which was occupied by the Macedons. It was here that he drank the poison and was burried in the sanctuary. The Sanctuary was also known at the antiquity for its role as capital of a religious association, Amphiktiony of Kalavreia. The sanctuary of Poseidon was served by many priests and always by a virgin priestess who, after her marriage, was replaced by another virgin.

In 50 BC the sanctuary was plundered by Cilician pirates, around 396 AD by the Goths and what remained was destroyed by the earthquakes as well as by the hands of ulteriors.

In 1774 a lot of porous and other processed stones were transfered to the bay of Vagionia and from there to Hydra for the reconstruction of the church of Virgin Mary.

Today, only a few foundations are rescued along with some plates with inscriptions on them to reveal the magnificence of the ancient sanctuary.

The whole area has been characterised as an archaeological site. Excavations were done for the first time at the sanctuary of Poseidon in 1894 by two Swedish archaeologists and continue until now.