Ancient Egyptian pyramids are shaped stone masonry structures. They are the best known pyramid structures, and are some of the largest ever buildings. Over 130 pyramids have been discovered in Egypt. Most were built on the western side of the River Nile in desert areas. Egyptian pyramids are often contain chambers and passages. The pyramids were built as the burial places of the Egyptian kings before the start of the old kingdom until the end of the middle kingdom. Because the Egyptians kept written records, we know about the building of some pyramids.