The sanctuary and the temple of Poseidon

The second temple's (the one that exists today) construction began in 449/8 BCE by order of Pericles. Local marble (Agrileza) was used and parts from the previous temple too. In order to lay the foundations, the hilltop was flattened. The construction was completed in 440 BCE. The dimensions were 31.12 × 13.47 m. The columns had a height of 6.1 meters and are 1 meter in diameter at the base and 79 cm at the top. The architect is unknown but probably is the one who also designed the temple of Hephaestus at the Agora in Athens, the temple of Ares (which in Roman times was moved to the Agora) and the temple of Nemesis in Rhamnous, as these four temples were almost identical to each other.

However, the temple of Poseidon had many innovations: it didn't have an interior colonnade in the cella making its capacity bigger. Also, the frieze was around all four sides of pronaos not just on the part above the entrance. Its subject was the Centauromachy, the Gigantomachy and the Labors of Theseus. There was no frieze on the west side nor an inner entablature. Finally, the metopes were left blanc without any decoration.

The entrance at the sanctuary area was a Doric portico which had three door openings. In the middle one there was a ramp. It was constructed shortly after the temple, out of marble and limestone. North and west inside the enclosure, there were two stoas in which the visitors of the sanctuary could rest.

The Temple of Poseidon was deserted during the Roman period. In recent years many parts of the temple were taken and transported either in museums or private collections. Thus, 5 column drums are in England at Chatsworth (and support the statue of the 6th Duke of Devonshire), 3 in Venice and 3 in Germany (Potsdam).