How were the pyramids of Egypt built?

The Pyramid of Khufu (sometimes called Cheops), the largest Egyptian pyramid, is made of 2.3 million stone blocks, each weighing anywhere from 2.5 to 16 tons. Some of the blocks, particularly the ones used in the inner chambers, came as far as Aswan, 500 miles from Giza where the pyramid stands. But how did ancient Egyptians build such massive pyramids without using simple machines such as the wheel, which, while used by Egyptians for pottery making, was not used for carts or chariots until 1500 BCE, likely because wheels weren’t much use in the thick sand that covered the country? It’s an age-old mystery and one that continues to be an enigma for ancient monumental complexes across the world. While there are numerous theories, there is a lack of hard, archaeological evidence to fully support any one of them.

One theory about how the blocks were moved involves sleds and wet sand. A painting in the tomb of Djehutihotep shows men dragging a colossal statue on a sled. In front of them, a person pours water onto the sand. While initially thought to be a ceremonial gesture, physicist Daniel Bonn recently discovered that the right amount of water, about two to five percent of the volume of sand, increased the stiffness of the sand and reduced the friction between the object being dragged and the ground, making the object much easier to move. The same technique may have been used to drag stone blocks to pyramid construction sites.

Once the blocks were at the pyramid’s construction site, however, how were they lifted into place without the use of mechanical advantage? A ramp found in a quarry dating to the construction of the Pyramid of Khufu indicates that ancient Egyptians were able to pull stone blocks out of the quarry on a steep upward slope. It’s possible that similar ramps were used to haul stones up the pyramid’s sides to be placed. However, the exact system is unknown. The ramps could have been on the outside of the pyramid, spiraling up like a mountain road, or straight and long, or built within the pyramid. How a 16-ton block could have been moved up a ramp is also unknown, with theories ranging from sleds to wooden rollers to wooden posts tied to each side of a block, changing the shape from square to polygon and allowing them to be rolled like a keg of beer.