All of them have four triangular sides sloping up from a square base. The shape symbolised the rays of the sun reaching down to Earth, with the polished sides reflecting the light. The shape also mimicked the primordial mound, which in Egyptian religion had been the first part of the Earth to emerge from the ancient waters.
Every pyramid was built on the West Bank of the Nile. This put them close to the setting sun and so to the mythological realm of the dead.
Archaeologists have currently identified a total of 118 pyramid tombs in Egypt. Most of these are relatively small and some of the poorly built ones have collapsed into a pile of rubble. As recently as 2008, the ruins of a pyramid emerged from sand dunes near Saqqara, so it is believed that other pyramids may exist that have not yet been found.
Answered by one of our Q&A experts, Rupert Matthews. For more fascinating questions by Rupert, and the rest of our panel, pick up a copy of History Revealed! Available in print and for digital devices.