The pyramid remained the tallest man-made structure in the world for over 3,800 years,[6] unsurpassed until the 160-metre-tall (520 ft) spire of Lincoln Cathedral was completed c. 1300. The accuracy of the pyramid's workmanship is such that the four sides of the base have an average error of only 58 millimetres in length.[7] The base is horizontal and flat to within ±15 mm (0.6 in).[8] The sides of the square base are closely aligned to the four cardinal compass points (within four minutes of arc)[9] based on true north, not magnetic north,[10] and the finished base was squared to a mean corner error of only 12 seconds of arc.[11] The completed design dimensions, as suggested by Petrie's survey and subsequent studies, are estimated to have originally been 280 royal cubits high by 440 cubits long at each of the four sides of its base. The ratio of the perimeter to height of 1760/280 royal cubits equates to 2π to an accuracy of better than 0.05% (corresponding to the well-known approximation of π as 22/7). Some Egyptologists consider this to have been the result of deliberate design proportion. Verner wrote, "We can conclude that although the ancient Egyptians could not precisely define the value of π, in practice they used it".[12] Petrie, author of Pyramids and Temples of Gizeh concluded: "but these relations of areas and of circular ratio are so systematic that we should grant that they were in the builder's design".[13] Others have argued that the Ancient Egyptians had no concept of pi and would not have thought to encode it in their monuments. They believe that the observed pyramid slope may be based on a simple seked slope choice alone, with no regard to the overall size and proportions of the finished building.[14]
In 2013 rolls of papyrus were discovered written by some of those who delivered stone and other construction materials to Khufu's brother at Giza.[15]