Why are Egyptian pyramids triangular in shape?

To shelter and safeguard the part of a pharaoh's soul that remained with his corpse, Egyptians built massive tombs-but not always pyramids.

Before the pyramids, tombs were carved into bedrock and topped by flat-roofed structures called mastabas. Mounds of dirt, in turn, sometimes topped the structures.

The pyramid shape of later tombs could have come from these mounds. More likely, Egyptian pyramids were modeled on a sacred, pointed stone called the benben. The benben symbolized the rays of the sun; ancient texts claimed that pharaohs reached the heavens via sunbeams.