Collapsed Pyramid at Medum 2637 BC - 2613 BC Medum, Egypt

The true (smooth) pyramid evolved in the third dynasty from its step pyramid predecessor. The Medum pyramid is an early example of this. It was constructed by filling in a seven-stepped core with loose rubble, the whole being then encased in smooth limestone. This pyramid collapsed in antiquity, because the casing was not bonded strongly enough to the core. Its engineering failure produced a uniquely instructive and appealing ruin.

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.