A form of Egyptian royal tomb, transitional between the mastaba of the early Archaic Period and the true pyramid of the Old Kingdom. Djoser's at Saqqarah is the only completed step pyramid known. The pyramid itself evolved through numerous stages from a flat mastaba (an oblong tomb with a burial chamber dug beneath it, common at earlier nonroyal sites) into a six-stepped, almost square pyramid (a terraced structure rising in six unequal stages to a height of 60 m, its base measuring 120 m by 108 m). The substructure has an intricate system of underground corridors and rooms, its main feature being a central shaft 25 m deep and 8 m wide, at the bottom of which is the sepulchral chamber built of granite from Aswan. The Step Pyramid rises within a vast walled court 544 m long and 277 m wide, in which there are remnants of other stone edifices.