The Great Pyramids of Giza were built around 4500 years ago, (give or take a few hundred years), so there is a great deal of mystery surrounding their construction, considering it was so long ago and the Egyptians at that time will have had no technology to assist them like we have today.
Many alternative, often contradictory, theories have been proposed regarding the pyramid’s construction techniques. Many disagree on whether the blocks were dragged, lifted, or even rolled into place. The Greeks believed that slave labour was used, but modern discoveries made at nearby workers’ camps associated with construction at Giza suggest that it was built instead by tens of thousands of skilled workers. Verner posited that the labour was organised into a hierarchy, consisting of two gangs of 100,000 men, divided into five zaa or phyle of 20,000 men each, which may have been further divided according to the skills of the workers. Some people even say aliens, but that requires a post of its own!
One mystery of the pyramid’s construction is its planning. John Romer suggests that they used the same method that had been used for earlier and later constructions, laying out parts of the plan on the ground at a 1-to-1 scale. He writes that “such a working diagram would also serve to generate the architecture of the pyramid with precision unmatched by any other means”. He also argues for a 14-year time-span for its construction. A modern construction management study, in association with Mark Lehner and other Egyptologists, estimated that the total project required an average workforce of about 14,500 people and a peak workforce of roughly 40,000. Without the use of pulleys, wheels, or iron tools, they used critical path analysis methods, which suggest that the Great Pyramid was completed from start to finish in approximately 10 years.
