The Erechtheion, built between 421 and 395 B.C. and thus the youngest feature of the Acropolis in its classical form, incorporates a number of very ancient sanctuaries, and its complicated ground plan reflects the need to take account of these earlier structures.
The eastern part was occupied by the temple of Athena Polias, patron of the city, with the ancient and much venerated wooden cult figure (xoanon) which had previously stood in the Old Temple of Athena, no doubt perpetuating cult traditions going back to the palace which occupied the site in Mycenaean times.
In the western part of the Erechtheion were the tombs of king Erechtheus, who gave his name to the whole structure, and Kekrops, the mythical founder of the Athenian royal line.
The tomb of Kekrops lay under the Porch of the Caryatids Caryatids which projects on the south side of the Erechtheion, its entablature borne by six figures of maidens in place of columns. On the north side is another cult feature.
An opening in the floor affords a view of the rock in which the ancient Athenians saw the trident wielded by Poseidon when contending with Athena for possession of Attica.
The east and north porticos each had six lonic columns, though the east portico now lacks one of its columns, which Lord Elgin carried off to London together with one of the caryatids and the rest of the "Elgin marbles".
The doorway leading from the north portico into the interior of the temple is a masterpiece of rich and delicate ornament. On the outer side of the cella wall, above elegant palmette ornament, is a frieze of gray Eleusinian marble on which were set white marble figures (originals in Acropolis Museum).
The building was altered during the Roman period, in particular the west side, which then received its two-story form. It suffered further alterations in the seventh century, when it became a Christian church. In 1463 the Turkish commandant of the fortress used it for the accommodation of his harem.
The result of these changes was that the interior lost its original division into the temple of Athena Polias to the east and the western part with the tomb of Erechtheus. Most of the exterior, with its delicate lonic ornament, has survived.
From the north portico a side doorway leads into the adjoining cult precinct of the Pandroseion, which in turn is adjoined on the south by the foundation walls of the Old Temple of Athena, lying under the Porch of the Caryatids. To the east of the Erechtheion stood the altar belonging to this earlier temple.