Giza.
A building site four and a half thousand years old.

Herodotus wrote of forced labour, and the image of slaves under the whip lasted into the films of the 20th century. Since 1988 Mark Lehner’s team has been excavating south of the Sphinx a town that belongs to Khafre and Menkaure: long dormitories for crews, bakeries with bread moulds, granaries, administrative buildings, overseers’ houses and bones of cattle, sheep and goats in quantities that point to regular meat rations. On the plateau above lie the tombs of the builders and overseers, with titles, names and the names of their crews.

Those who are buried, eat beef and have their names written in a tomb are not slaves in the ancient sense. The pyramids were built by Egyptians whom the state drew from the villages for months, fed and organised in crews with names of their own, together with craftsmen who lived on site permanently. The labour was an obligation, but it was paid, in bread, beer and meat.

In 2013 Pierre Tallet and Grégory Marouard found at Wadi al-Jarf, a harbour of Khufu on the Red Sea, papyrus fragments in sealed storage galleries: the oldest inscribed papyri in existence. Two of them are the logbook of an overseer named Merer from Khufu’s 27th regnal year. Day by day he records how his crew of about forty men loaded limestone at Tura, sailed in two days to Akhet Khufu, unloaded and returned, usually three trips a month, as well as stays with an official named Ankhhaf, the king’s half-brother, who directed the works.

For the first time an administrative document from the construction itself exists. It confirms what Lehner had read from the terrain: transport ran by water, along canals and harbour basins to the foot of the plateau, and the casing was applied in the last years of construction. The reckoning of twenty years of building gains a frame from the papyri; more than one crew and one year they do not show.

Herodotus described lifting devices of short timbers, Diodorus an earthen ramp. Modern proposals range from a single straight ramp through spiral ramps on the outside to Jean-Pierre Houdin’s ramp inside the pyramid. In 2018 teams from the IFAO and the University of Liverpool found in the alabaster quarry of Hatnub a ramp from Khufu’s reign: a central track with stairs on both sides and post holes around which ropes were redirected to haul sledges up slopes of more than twenty percent.

Hatnub shows that the Egyptians of the Old Kingdom knew steep ramps with turning posts; with these, shorter ramps could be built on the plateau than previously calculated. For the top courses every ramp remains a problem, which is why many researchers assume a combination: a straight ramp below, levering and hauling on the steps above. The void of 2017 could, on one reading, belong to an internal construction feature.

The sides of Khufu’s pyramid deviate on average only about three arc minutes from true north; Petrie measured this from 1880 to 1882 with theodolite and steel tape and found the plan square to within a few centimetres. In 2000 Kate Spence showed in Nature that the deviations of the Old Kingdom pyramids fall into a sequence: the Egyptians probably sighted two stars circling the same point at the moment both stood vertically one above the other, and because the earth’s axis slowly wanders, so did the error. From it Spence derives a construction date around 2480 BCE with an uncertainty of five years.

The precision was no accident but surveying with the sky as reference. Whether it was exactly the two stars Spence proposes is disputed; that the Egyptians fixed north astronomically is not. The plan you walk around at the foot of the pyramid was laid out in a night with plumb line and sighting rod.

Since 2015 the ScanPyramids project, a collaboration of Cairo and French institutes with physicists from Nagoya, has been measuring cosmic muons falling through the pyramid; where stone is missing, more arrive. In 2017 the team reported in Nature a void at least 30 metres long above the Grand Gallery, confirmed by three independent detector types. In 2023 followed, in Nature Communications, a corridor nine metres long behind the gable of limestone blocks on the north face, which was also filmed with an endoscope.

The pyramid is not as solid as it looks. What function the large void had is open: a relieving space like that above the King’s Chamber, a remnant of the building technique, or a room nobody was meant to enter. The corridor on the north face probably distributes the load above the entrance. Both are clues to how the builders planned the interior, not to treasure.