Collapsed Pyramid at Medum
2637 BC - 2613 BC
The true (smooth) pyramid evolved in the third dynasty from its step pyramid predecessor. The Medum pyramid is an early example of this. The intent was to add fill around a seven-stepped core, then encase the whole pyramid in smooth limestone. But it was abandoned before completion, probably due to some kind of engineering failure (exactly why, is not known). Its valuable limestone blocks were taken away and reused; only the exposed core remains today, surrounded by a great heap of sand and rubble. (The sand was not part of the pyramid, but simply blew in from the surrounding desert.)
The pyramid was probably built by Huni, the last king of the third dynasty, and finished by his son Snefru, the founder of the fourth Dynasty. Medum is about 40 miles south of Giza, between the Faiyum oasis and the Nile.