The Pyramids were constructed to hide the tombs of the Pharaohs. The first pyramids were step pyramids to help the pharaoh climb the steps and join the sun god Ra in the sky. After that (about 4,500 years ago) came the biggest pyramids of all, the pyramids of kings Khufu and Khafre. Until about a hundred years ago these pyramids were the tallest structures in the world! No earthquake could destroy them. They were each built of more than 2 million blocks of stone, which each weighed about as much as a small elephant. The limestone coverings were stripped by later peoples for building use. In the pyramids were a lot of false doors to trick grave robbers but they didn't work!