What is a pyramid?
A pyramid is a geometrical solid with a square base and four equilateral triangular sides, the most structurally stable shape for projects involving large amounts of stone or masonry. Pyramids of various types, sizes and complexities were built in many parts of the ancient world (like Central America, Greece, China and Egypt). In the history of Egypt and China, they were primarily tombs and monuments to kings and leaders. The pyramids of the Mayans and Aztecs of Central America were mainly religious temples, though some of them housed burial chambers. The Central American pyramids were smaller and sometimes wider than their Egyptian counterparts. These pyramids also took longer to finish -- they were often built and modified over hundreds of years, while Egyptian pyramids took a couple of decades to construct. Pyramids in Central America were integrated into Aztec and Mayan cities, whereas Egyptian pyramids were located away from the major cities.
 © Photographer: Ivan Freaner, SXC A Mayan pyramid at Chichen Itza, Mexico. See more pictures of pyramids. |
The ancestors of these great structures are the burial tombs found throughout North America and Europe -- simple mounds of earth that covered burial chambers. The first tombs of the Egyptian pharaohs were flat, box-shaped buildings called mastabas (Arabic for "bench"). Pharaohs later built grander tombs by adding levels on top of the box to form stepped pyramids. Stepped pyramids are prevalent in Central America. In Mesopotamia, they were called ziggurats.
The Egyptians took pyramid design to new heights, culminating in the construction of the pyramids of Giza in the 26th century B.C. Laborers used 2.3 million blocks of limestone and granite to build the Great Pyramid of Khufu, which stands 146 meters high, has a 230-meter-square base and weighs about 6.5 million tons. A number of pyramids, including the Great Pyramid of Khufu, have survived thousands of years of exposure to the elements, a tribute to the ancient architects, engineers and workers who built them.
Egyptian Pyramids
The first stepped pyramid in Egypt, in Saqqara, was completed in 2620 B.C. for the Third Dynasty Egyptian pharaoh Djoser. It had four levels and an underground burial chamber. Builders later attempted, but never finished, another six-level stepped pyramid.
The Egyptians continued to construct taller and taller pyramids and started smoothing out the jagged edges of stepped pyramids. One of the earliest attempts was the Meidum pyramid, in 2570 B.C. It had seven steps progressing to eight, but it collapsed and was abandoned.
Bethany Carlson, SXC
The stepped pyramid of Djoser. See more pictures of Egyptian pyramids.
Pyramid designers learned that if pyramids were going to be higher and have steeper slopes, their bases needed to be wider. At Dahshur, further upstream along the Nile from Saqqara, laborers started the construction of a pyramid for the Fourth Dynasty pharaoh Sneferu. Unfortunately, the designers chose a poor foundation, and the pyramid began to lean inward upon itself when it was about two-thirds complete. The builders reduced the angle of the upper portion to complete it and make it more stable, and it is now known as the Bent Pyramid (2565 B.C.).
Unsatisfied with the Bent Pyramid, Sneferu ordered another pyramid at Dahshur. The designers chose a better foundation and made this pyramid the same height as the Bent Pyramid, but with a wider base and a shallower angle. The Red Pyramid was completed in 2560 B.C.
The Great Pyramid of Khufu
The Giza pyramid complex, on the west bank of the Nile, is the most famous group of pyramids in the world. As we discussed earlier, the grandest pyramid was built for Sneferu's son, Khufu, in 2540 B.C. The two smaller pyramids nearby were for Khufu's son, Khafre, and his grandson, Menkaure. After this dynasty, great pyramid building stopped, probably because of the time and expense of these massive state projects.
The Great Pyramid of Khufu on the Giza plateau in Egypt is the largest and most elaborately constructed pyramid in existence, representing the most advanced aspects of pyramid construction. Khufu's pyramid has the following features:
- The primary burial chamber, or king's chamber, contains the sarcophagus (tomb) that held Khufu's body, and the walls are adorned with hieroglyphs (writing) depicting various aspects of ancient Egyptian history and religion.
- The smaller queen's chamber (actually a misnomer -- it was not intended for the queen) lies within the pyramid, while another unfinished secondary burial chamber lies underneath the pyramid.
- Weight-relieving chambers above the king's chamber distribute the weight of the overlying rock and prevent the king's chamber from collapsing.
- The gallery is a large passageway with a vaulted, corbelled ceiling (the walls are layered upward, and each vertical layer sticks out further than the one below to form a primitive arch).
- Descending and ascending passageways connect various chambers to each other and to the outside.
- Air shafts connect the king's chamber to the outside. They may have been designed as a way for Khufu's spirit to exit the pyramid and rise to the heavens.
- The entrance was sealed after the pharaoh's body was placed inside.
- White limestone rocks line the pyramid's exterior, giving it a smooth face. These rocks have eroded away over time, but we know they existed because the Pyramid of Khafre still has some on its peak.
How Were the Pyramids Built?
Pyramid construction is a continuously debated topic. There are no existing records of building plans or discussions of construction methods, so no one knows exactly what happened. Of course, archaeologists and engineers have plenty of ideas -- some sound far-fetched and others seem more reasonable. We'll use the Giza pyramids as an example because we have the most information on them.
Let's break the task of building the pyramids into components:
- Surveying and excavation: choosing a suitable site, orienting it and preparing the foundation
- Obtaining building materials: quarrying rocks or making huge stones
- Transporting building materials: transporting from the quarrying site to the pyramid
- Workforce logistics: finding skilled workers, feeding them and housing them
Surveying and Excavation
Egyptian builders probably made plans and models of the pyramid. The projects were overseen by the pharaoh's master builder, or vizier.
The collapse of the Meidum pyramid and the shift of the Bent Pyramid taught builders that foundations were important. Once engineers found a suitable site with a good foundation, they had to lay out the site. Pyramid sides always ran parallel to the north-south and east-west axes. The builders didn't have compasses, and there was no North Star at the time (the Earth's rotation wobbles like a top, and the position of true north in the sky changes over a 40,000-year cycle). So, they used the movements of circumpolar stars or the sun to figure out true north. Using sighting rods and circles, they could trace arcs of the rising and setting stars or the sun's shadow, measure the angles to the ends of the arc, and calculate true north. Once they established that, they could find the other directions with lines and right angles.
© Photographer: Foxie_aka_ashes | Agency: Dreamstime
The Great Sphinx sits in front of the Pyramid of Khafre
on the Giza plateau in Egypt.
The ancient Egyptians used "cubits" (the length from the tip of your middle finger to your elbow) and "hands" (the width of your hand with the thumb on the side) for measurements. They dug post holes at regular intervals (10 cubits) along the base outline and laid out the site in a grid.
Then, laborers excavated and leveled the foundation. No one is sure of the exact method, but they were extremely exact -- the base of Khufu's pyramid is level to 2 centimeters (less than an inch).
There are two main theories about leveling methods:
1) Workers poured water into the excavated site and leveled all material above the waterline. Then they lowered the water level and removed more material, continuing the process until the foundation was level.
2) The builders installed posts at regular intervals. A line, leveled with plumb bobs, was pulled taut across the posts at a reference mark to ensure alignment. Then they could excavate the foundation down to the reference marks.
Once the foundation preparation was finished, the grunt work could begin.Heavy Lifting
Obtaining building material
The pyramids were built of limestone, granite, basalt, gypsum (mortar), and baked mud bricks. Limestone blocks were quarried at Giza and possibly other sites. Granite likely came from upriver at Aswan. Alabaster came from Luxor and basalt from the Fayoum depression.
Iron tools were not available, so workers used copper and stone-cutting tools to carve out the blocks in the quarries. They then used levers to move the stone blocks away from the quarry site.
 © Photographer: Pomortzeff | Agency: Dreamstime The Bent Pyramid at Dahshur, Egypt |
Again, no one knows how laborers were able to get the 2.5-ton stone blocks from the quarries to the building site. Wheels wouldn't have been useful on the desert sand and gravel, so they most likely dragged the blocks with wooden sleds and ropes. Some think that workers used quarter-circle wooden sleds that fit around a rectangular block. They attached the sleds to the block, and a crew of about eight men rolled them along the ground, much like rolling a keg of beer. Others say the laborers used wooden rollers.
For long-distance transport, the blocks were loaded on barges and transported down the Nile. Workers dug canals to get the barges nearer to the site.
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While laborers placed stones in the core, stone cutters were making the chambers, passageways and shafts in the pyramid's interior. Artists inscribed the designs that adorned the chamber walls. Let's take a closer look at the workers who built the pyramids.
Workforce
The Greek historian Herodotus described the building of Khufu's pyramid by more than 100,000 slaves. Hollywood seized upon this image of slaves and their taskmasters in movies like "The Ten Commandments." But when Harvard archaeologist Mark Lehner led an expedition to uncover clues about the people who built the pyramids, he found no evidence of housing for such a large population. Instead, his group discovered housing and food storage places for small gangs of workers. It appears that at any one time about 2,000 workers were on site, divided into two large divisions and smaller groups of about 200 men. The evidence indicates that they were probably paid and well fed. The working groups were periodically rotated over the years of pyramid construction, and the total workforce may have been about 30,000 [source: Harvard Magazine].
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