The pyramid of Khufu, originally 147 meters high, is estimated to have been constructed with between 5 and 6 million tons of blocks transported from the quarries on sleds and ramps without the benefit of wheels. It and other pyramids were aligned accurately to a north-south axis using the midway position of a northern star for measurement. The pyramids maintained a precise angle of incline without twisting using peg and chord technology, but probably without geometry. The construction is so amazing that Khufu's pyramid was one of the seven wonders of the ancient world and is the only one still standing today.
Sources:
"The Periodic System of Building a Pyramid," by Alexander Badawy. The Journal of Egyptian Archaeology, Vol. 63, (1977), pp. 52-58.
"The Geometry of Zoser's Step Pyramid at Saqqara," by Rory Fonseca. The Journal of the Society of Architectural Historians, Vol. 45, No. 4 (Dec., 1986), pp. 333-338.
More on the Giza Pyramids and How Tall Was the Great Pyramid?.
