the temple of Athena and Poseidon-Erechtheus on the Acropolis in Athens, an outstanding monument of ancient Greek architecture. Built between 421 and 406 B.C., it has an asymmetrical spatial composition and comprises a number of rooms, two Ionic porticoes, and the famous Porch of the Maidens. The Erechtheum is impressive for its exquisite composition and individual details. Although modest in size, occupying an area (without porticoes) of 11.6 m × 23.5 m, it plays an important role in the Acropolis complex, contrasting with the simpler and more austere Parthenon.