North of the Parthenon is the second large temple on the Acropolis, the Erectheion, which is somewhat later. Its construction started in 421 BC, was halted for the Sicilian Campaign and was completed in 405 BC. Its architect is unknown even though many have maintained it was Mnisikles. From an inscription of 409 / 408 BC we know the name of Philoklis as the architect who supervised the works at this stage.
Erectheion is a complex and completely original structure. Its name shows it to be the dwelling of Erectheos and it corresponds to a complex temple building.
Its architectural peculiarities were the result of the endeavor to leave certain points with religious meaning untouched as well as the as the endeavor to have a variety of uncommon forms of worship coexisting in the building at one and the same time.
It was pillared building with six columns on the facade. Internally divided by a transverse wall into two parts which do not communicate with each other. The two sections of the shrine had a difference of three meters in height and did not communicate with each other. The west side of the building was not enclosed by a wall but had five openings separated by railings with four intermediary Ionic columns which during the Roman period were converted into windows.
To the south was the Porch of the Caryatids which was built on the tomb of Kekrops, with six Kores statues which rest on the high continuous base and gracefully support the entablature, and the marble roof. Five of the statues, which today have been replaced by plaster casts, are found in the Acropolis Museum and one in the British Museum.
On the north side of the west part of the structure a four – pillared entrance porch was fashioned in a u shape with six Ionic columns.
The entrance door from the north porch into the west apartment of the shrine was particularly well crafted. The door, adorned with repeated and profusely decorated motifs, large rosettes and two cornices to the left and the right, is a marvelous example of what the Ionic style was like at the end of the 5.
Investigators have formulated a number of views regarding the various areas of worship in the Erectheion. According to the most prevalent one: the eastern section must have been dedicated to Athena to which the effigy of the goddess had been transferred part from the older temple while the western must have been used for the worship of Erectheos as well as Hephaestus and the hero Voutos. The main part of the temple ‘s sculptural decoration has been lost. The frieze was made of plaques of dark – colored Eleusinian stone on which were secured the relief figures made of pentelic marble.
The motifs on the frieze have not been clearly deciphered. They most probably reflected the local myths of the town. On the pediments were found the birth of Athena from Zeus‘ head and the dispute of Poseidon and Athena over the rule of Attica. Near the Erectheion is the entrance or the exit of the passage to the Cave of Aglauron Athena where according to mythology the goddess’ sacred snake entered and left the Acropolis.