The pyramids are the most iconic and impressive features of ancient Egypt. They are giant monuments that have enthralled visitors ever since. Because of their great size and their great age, they have also been subject to wild speculation and misinformation. Among the more outlandish claims is that the pyramids were built by extra-terrestrials, as if ancient people from North-Africa would somehow be incapable of constructing these edifices.
Academically trained archaeologists have studied the pyramids for decades. The ancient Egyptians built the pyramids using techniques and tools that are familiar to modern construction workers (Stocks 2003, pp. 25-73). The tools may have been simpler, and the work more labour-intensive and time-consuming, but the pyramids were the result of human sweat and elbow grease. The skills used in building the pyramids were refined over the course of centuries, subject to a process of trial and error, and also put to use in other monumental building projects, including temples and the erection of colossal statues.
The pyramids were monumental structures that served as the tombs of kings. A burial chamber was located either inside the pyramid or underneath it. The very first pyramids, starting with the one of Djoser at Saqqara (ca. 2670 to 2650 BC), were step-pyramids. In other words, they did not have a smooth sloping side, but were made of a series of tall squares, superimposed and progressively smaller.
The other pyramids of the Third Dynasty were made of inward-leaning accretion layers (Stocks 2003, pp. 13 and 20), while the other pyramids of the Old Kingdom (ca. 2600 to 2100 BC), like the ones at Giza, consisted of a core of superimposed rectangles, covered by a smooth outer casing, while the later ones had a core of masonry, followed by a layer of backing stones, covered by the outer stone casing. True innovation arrived during the Middle Kingdom (ca. 1975 to 1640 BC), when the pyramids were built with a core of mudbrick and an outer casing of stone (Lehner 1997, p. 226).
Moreover, adjustments made during the construction of pyramids can still be seen in some cases, where the inclination of the slope was slightly modified to be corrected on its way to the top. There are also pyramids that were abandoned during construction, such as the so-called Unfinished Northern Pyramid of Zawyet El Aryan perhaps because of problems that arose while they were being built and which could not be fixed. Such mistakes demonstrate how pyramids are very clearly the products of human hands.
Acquiring the stone
A pyramid consists essentially of huge stone blocks. For the most part, these blocks were made of stone that was readily available near where they were built. Or to put it another way, it may well be that the pyramids were constructed near the sources of stone (Lehner 1997, pp. 206-207), such as at the Giza Plateau. Granite and basalt blocks often had to be quarried elsewhere and then transported to where they were needed (e.g. Aston et al. 2000, pp. 17-18).
The ancient Egyptians had a lot of experience when it came to quarrying stone. Stone was needed not only in the construction of the pyramids, but also to build temples and to create statues and obelisks. In the case of the stones needed for the pyramids, the quarries were mostly shaped like galleries excavated in the escarpment (see also Aston et al. 2000, p. 6ff). Blocks were cut using wood, stone, and copper tools, broken from their bases using large wooden levers, the traces of which are sometimes still visible on the blocks.
For extremely hard stone, such as granite and basalt, copper hand drills or saws were used in combination with an abrasive mixture of water, quartz sand, and gypsum. From the granite quarries at Aswan, pear-shaped dolerite pounders have been found. These weighed between 4 and 7kg and had to be used with both hands. As they wore out, they came rounded and were then reused as rollers and pivots, some of which have been found underneath stone sarcophagi.
How did the ancient Egyptians move these massive blocks of stone? Some archaeologists believe that the blocks were put on a sledge. Wooden logs (rollers) were put underneath the sledge, and a path would be created with a surface of gypsum or hardened clay, to prevent the block from sinking into the sand. Workmen pulled the block using ropes, and other workmen would move rollers from the back of the sledge to the front to keep it going.
The problem with this hypothesis is that it would entail quite an investment in wood, which is scarce in Egypt. Another, more likely possibility, is that the sledge was pulled on artificial slideways, i.e. on artificial inclined ramps. Traces of these ramps have been found at Lisht and they are also depicted in wall-paintings in tombs. The ramps were made of debris with a roadbed of wooden crosspieces on top.
In both cases the important thing was to moisturise the ground to ease the movement of the wooden logs and of the sledge. Workmen wetting the ground with water are represented in tomb paintings, for example in scenes depicting the transportation of a colossal statue, such as the relief from the tomb of Djehutihotep in el-Bersheh. According to experiments, a team of twenty people could easily pull a 2.5 ton block across a sliding surface, and on a levelled and moisturised surface each hauler could support one-third of a ton.
And what about the block coming from further away, even from Aswan? The block was put on a sledge and then pulled on rollers or on earthen embankments onto a barge. Wall-paintings from tombs show, for example, the transportation of columns, on wooden beams and sledges, on barges. The stones were then brought up along the river Nile and then taken to the construction site, which was reached through canals that connected back to the Nile (Lehner 1997, pp. 202-203). For example, the Giza Plateau had a small harbour and could be reached through just such canals.
Building the pyramids
Constructing the pyramids required precise engineering (Olsen 2010, p. 28). But even with tools simpler that the ones we have today, the precision needed could be achieved. A pyramid is essentially a cube with sides meeting in the centre, or you can see it as a succession of smaller rectangles one stacked above the other, especially in the case of the big, “true” pyramids at Giza. In other words, to start building a pyramid, all you needed was to start with a single rectangle as a base.
To ensure that the starting rectangle had straight angles, the ancient Egyptians had a number of options available to them. They could use corners made of wood: one leg of the set square would be set along the already established side of the pyramid and its perpendicular would be drawn, then the set square would be flipped and the perpendicular drawn again, to ensure the least margin of error.
Another way is establishing a triangle like the Pythagorean one, a method that we may be able to recognize from the mortuary temples of the time. The third and final way would be to draw two circles on the already established side, by using a cord of the same length connected to a pole, and then to detect the angle given by the two lines crossing in the intersection given by the two circles.
An important step was setting straight lines for the square. To do this, first the true north had to be calculated. There are two possible ways to achieve this. The first one involves looking at the night sky: someone would stand inside a circular wall, to watch the night sky with a clear horizon, then would record the rising and setting point of a star. Bisecting these two points would indicate true north.
The second one uses the shadows given by the different positions of the sun: one would use a gnomon, or a pole with a plumb bob (to make it absolutely vertical), and record the length of its shadow three hours before noon, then mark were the shadow would end in the afternoon, and the true north could be derived by bisecting between these two points. However, the second method is tricky, because light conditions change throughout the year.
As the pyramids rose, the rectangles that they were made of needed to become smaller. This required correct calculation of the slope of the pyramid. Furthermore, the external ones had to be cut in a way as to give a smoothly inclined surface for the side. For each layer first the corner stone would be laid, and from there the two at its sides. The blocks were set in place by sliding them on wood logs. The smooth surface of the pyramid was made by fitting blocks and chiselling them into shape using copper chisels. These tools had to be sharpened often: the points where the chiselling had to stop for the tool to be sharpened are still visible on the blocks in some cases, and on this basis it has been calculated that a full-time re-sharpener was need for every one hundred men working in a pyramid.
As the pyramid was built, ramps were used to carry blocks up to higher levels (Lehner 1997, pp. 215-217). There are various suggestion for the shape of the ramps, starting from variations on ramps perpendicular to the pyramid, ending at the corners or at the centre of the side, or even inside the pyramid. However, such types of ramps would simply become too long if they were to reach the upper layers. It is also possible that the ramps would have zig-zagged along one of the sides, or wrapped around the pyramid; there may even have been a system of ramps where the number decreased the higher up the pyramid you went. More likely, some combination of these methods was used.
The top of the pyramid was no doubt the hardest to get right. There was less room to manoeuvre here, and limited space for ramps. In some cases, the stone directly underneath the capstone – referred to as the pyramidion – is shaped like a reverse triangle and was encased in another, concave-shaped, stone (Lehner 1997, pp. 222-223).
The workforce consisted of a nucleus of specialized and skilled builders and craftsmen who were permanently employed by the king. The bulk of the workers consisted of conscripted peasants, i.e. farmers who would work on the pyramids when they had little in agricultural work to do (Lehner 1997, pp. 224-225). The workers did not include slaves. The workforce were often housed in towns sometimes deliberately founded near the construction site (e.g. Stocks 2003, p. 25).
The conscripted labour force worked on the pyramid in three-month shifts. A shift could consist of 25,000 men in total (cf. Stocks 2003, p. 198), which included not only the people quarrying, hauling, and setting the stones, but also metal-workers and other tool-makers, potters, brewers, and bakers, water-carriers, and other specialists who needed to take care of all the necessities required by a large group of people working together.
The workmen hauling, setting, and casing the stones were divided into gangs, which were part of two larger divisions. The workmen hauling and setting the stones may have numbered around 2,000 souls, divided into two teams of a thousand people each, each divided into five yet smaller gangs of around 200 people each.
Based on experiments, it has been calculated that a team of slightly more than 1,200 workmen would have been enough to quarry the 322m³ of stone needed every single day to build Khufu’s pyramid at Giza – also known as the pyramid of Cheops, the Hellenized form of Khufu – over the course of his 23-year reign. Considering that the other pyramids were smaller and hence would have required fewer men, this amount of people appears reasonable, and shows that the construction of the pyramids could be achieved by a highly-organized society such as that of ancient Egypt.