The principal entrance to the Acropolis is a monumental gateway called the Propylaea, which is made of white marble. It is located at the western end of a walled enclosure near the top of the Acropolis, at the head of a steep, winding path. It was begun in 437 BC, but work on it stopped five years later, probably because of a threat of war. The Peloponnesian War, between Athens and an alliance led by Sparta, finally broke out in 431 BC. Sparta’s alliance defeated Athens, and the Propylaea were never completed.
The Propylaea was designed by Greek architect Mnesicles to have a central section with wide openings and two wings, one to the north and the other to the south. The facade of the central section consists of six widely spaced columns in the simple Doric order (style). Inside, two rows of columns in the more elegant Ionic order divide the central area into three sections through which visitors proceed. The north wing was to house a gallery of paintings, and the south wing was to provide a passageway to the Temple of Athena Nike. The wings of the Propylaea were never completed.