The great pyramids were built by the ancient Egyptians as tombs. The largest of the pyramids was built around 2500 B.C. for the pharaoh Khufu. Until the 20th century, it was the largest building in the world.
In the past, widespread belief was that the Egyptians used slave labor to build the pyramids. Later archaeological evidence suggests that the pyramids were constructed by a special class of people who were housed, fed and organized into rotating teams. Evidence also suggests that fewer people were needed to build the pyramids than originally thought. By wetting down the sand in front of the stones, workers could manipulate heavy loads much more easily.