The pyramids at Giza were built as massive tombs for three pharaohs - Khufu, Khafre and Menkaure. The mummified body of each pharaoh was placed in the burial chamber, deep in the heart of the pyramid. This was to protect it from the hot sun and from the grave robbers. The ancient Egyptians put many other things in too, such as food, furniture and pets, because they believed the dead person would need these in the afterlife. Thousands of workers were needed to build Khufu's Great Pyramid. Between 5,000 and 20,000 worked on the building of the pyramid, most of them farmers who were called up to work during the flood season. It took about 20 years and 2.3 million blocks of stone to build it. Originally, the pyramids were covered in a smooth surface of white limestone, which would have been dazzlingly bright under the Egyptian sun.