It's long been a hotly debated open question regarding how the great pyramids of Egypt were built, given the sheer size and weight of the limestone blocks used for the construction. Numerous speculative (and controversial) hypotheses have been proposed, including the use of ramps, levers, cranes, winches, hoists, pivots, or any combination thereof. Now we can add the possible use of a hydraulic lift to those speculative scenarios. According to a new paper published in the journal PLoS ONE, ancient Egyptians during the Third Dynasty may have at least partly relied on hydraulics to build the Step Pyramid of Djoser.
"Many theories on pyramid construction suggest that pure human strength, possibly aided by basic mechanical devices like levers and ramps, was utilized," co-author Xavier Landreau, of Paleotechnic in Paris and Universite Grenoble Alpes, told Ars. "Our analysis led us to the utilization of water as a means of raising stones. We are skeptical that the largest pyramids were built using only known ramp and lever methods."
The Step Pyramid was built around 2680 BCE, part of a funerary complex for the Third Dynasty pharaoh Djoser. It's located in the Saqqara necropolis and was the first pyramid to be built, almost a "proto-pyramid" that originally stood some 205 feet high. (The Great Pyramid of Giza, by contrast, stood 481 feet high and was the tallest human-made structure for nearly 4,000 years.) Previous monuments were made of mud brick, but Djoser's Step Pyramid is made of stone (specifically limestone); it's widely thought that Djoser's vizier, Imhotep, designed and built the complex. The third century BCE historian Manetho once described Imhotep as the "inventor of building in stone." As such, the Djoser Pyramid influenced the construction of later, larger pyramids during the Fourth, Fifth, and Sixth Dynasties.
Using limestone was a much more labor-intensive process than constructing mud-brick monuments. Unfortunately, there just aren't many historical sources from this period to shed light on how these pyramids were built. Herodotus in the fifth century BCE—centuries after the great pyramids were built—described the use of a machine consisting of one or more levers to raise blocks of limestone. In the first century BCE, Diodorus Sculls mentioned the use of earthen ramps, claiming that "machines for lifting had not yet been invented in those days."
Archaeologists have found evidence for the use of small ramps and inclined causeways at the Great Pyramid of Giza, among others, but it's likely other supplementary methods or devices were used, with levering believed to be among the strongest candidates.
Perhaps most controversially, French architect Jean-Pierre Houdin constructed an archetypal model of the Great Pyramid of Giza to demonstrate how an external ramp could have been used to build the first 30 percent of the structure, before switching to an internal ramp to move stones higher up. He explained the lack of evidence for such ramps by suggesting that the external ramp stones had been recycled to build the upper levels. (The 2017 video game Assassin's Creed Origins incorporates Houdin's controversial theory in its virtual tour of the Great Pyramid.) It's worth noting that Egyptologist David Jeffreys of University College London once dismissed Houdin's hypothesis as "far-fetched and horribly complicated," and it remains unproven.