The Erechtheion is the strange, asymmetrical temple on the north side of the Acropolis, built between 421 and 406 BCE — after the Parthenon was finished — and designed to incorporate the most sacred shrines of pre-classical Athenian religion. Its irregular plan reflects the multiple holy sites it had to house on different levels of the bedrock.
Its most famous feature is the Porch of the Caryatids: six female figures who serve as columns. Five of the originals are in the Acropolis Museum; the sixth — taken by Lord Elgin in 1801 — is in the British Museum. The figures on the porch today are casts. The columns of the main building are among the most refined examples of the Ionic order in existence, with capitals carved to a precision unmatched elsewhere.