The Erechtheion was built in 420-406 BC on the part of the Acropolis held to be the most sacred; the place where the goddess Athena caused the most sacred emblem, the olive tree to sprout.  In contrast to the Parthenon, the Erechtheion was built in the Ionic style, much lighter and graceful.  It's a very complicated building on two levels, and is asymmetrical with two main porches that have no relationship to each other.  These dissimilarities are explained that the temple was dedicated to different gods.  The eastern part to Athena and the western to Poseidon-Erechtheus.  The projecting porth of the maidens (Karyatids) that one sees on the south is the most famous part of the temple complex.  The Karyatids are maidens who support the roof on their heads. The temple complex is divided into two sections: the eastern part contained the altars and the thrones of gods, and the western part contained the ancient wooden statue of Athena, and the grave of Erechtheus (both of which were in underground chambers.).  During the Middle Ages the Erechtheion was converted into a church and was used later as a harem when Athens was ruled by the Turks.