From F. Krefter’s Die Persepolis Rekonstruktionen

Persepolis’s palaces, audience halls and other royal buildings were constructed on a huge, multi-terraced platform. Roughly a quadrilateral, 1,500 feet on the west side, 1,000 feet on the north side, 1,400 feet on the east side, and 950 feet on the south side, the platform consists of a thick outer retaining wall filled in with debris. Visitors entered the citadel through a monumental double-reversing stairway built by Darius’s son and successor, Xerxes (486–465 B.C.), shown at far left in the drawing. The buildings visible in both the drawing and photo along the edge of the 60-foot-high western facade are, from right to left, the Palace of Darius and the Apadana.