Pharaohs used pyramids as burial chambers for their mummified bodies. Ancient Egyptians believed that when a pharaoh died, he transformed into the king of the dead and needed to be buried with his material possessions from this life.
Khufu's pyramid is 481 feet tall. Khafre's measures 471 feet and Menkaure's is 213 feet tall.
According to National Geographic, it took between 20,000 and 30,000 people over eighty years to build all three pyramids. The construction of Khufu's pyramid began around 2550 BC.
Slaves did not build the pyramids as was once popularly believed. Archaeologist Mark Lehner thinks that ordinary Egyptians built the pyramids under labor obligations not unlike those which existed in feudal Europe in the Middle Ages.
In 2002, archaeologists used the Pyramid Rover, a small robot, to explore a shaft of the Khufu pyramid. The robot drilled a small hole through a limestone door and inserted a camera only to reveal that a second door blocked the view.
