The construction of the Erechtheion began in 421 BC, during a period of truce known as the Peace of Nicias, which took place in the midst of the Peloponnesian War. This temple was erected as a replacement for the ancient archaic temple of Athena, which had been destroyed by the Persians during the Medical Wars.

The Erechtheion consists of a central building with an irregularly shaped ground plan that adapts to the sloping terrain. This building has two separate unconnected parts: on the east side is a sanctuary dedicated to Athena, in hexastyle style, with columns of Ionic order. On the other side, on the west side, it was composed of two chapels with double cults: one dedicated to Erechtheus and Poseidon, and the other to Hephaestus and Butes. Between these rooms was located the salt water fountain, which, according to legend, Poseidon made spring up with a blow of his trident during a dispute with Athena. In addition, the Erechtheion includes a stoa in its northern part, with columns, and in the southern part is the famous Tribune of the Caryatids, with six columns depicting female figures 230 cm high. These sculptures were made by Callimachus, a collaborator of Phidias. The Caryatids that can be seen at the site are replicas of the five originals that are in the Acropolis Museum, along with a sixth that is in the British Museum.

The Erechtheion featured a frieze adorning the sides of the building, composed of marble figures mounted on black limestone slabs from the city of Eleusis. One of these slabs has been preserved from the second phase of construction, on which one can read the names of the 130 workers who participated in the work, as well as their salary, which consisted of one drachma per day, the same remuneration received by the architect.