How Pyramids Work

The first stepped pyramid in Egypt, in Saqqara, was completed in 2620 B.C. for the Third Dynasty Egyptian pharaoh Djoser. It had six 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.

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.

Pyramid construction reached its apex with the Great Pyramid of Khufu. We'll learn all about it on the next page.

The Great Pyramid of Giza, also known as the Pyramid of Khufu, is the oldest pyramid in the Giza Plateau and is the only one of the Seven Wonders of the Ancient World still standing. It was built for Pharaoh Khufu around 2600 B.C.E. 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 Giza 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:

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:

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.

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:

Once the foundation preparation was finished, the grunt work could begin. We'll learn on the next page how the laborers transported the pyramid stones and put it into place.

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.

Transporting building materials

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.

Egyptologists estimate that workers placed­ about 300 stones a day during pyramid construction. Several theories -- lever systems, ramps and kites, for example -- attempt to explain how the huge blocks got into place. Those in the know generally accept the ­ramp idea, but they debate the exact ramp configurations. The ramps could have been long and straight, perpendicular to the sides or wrapped around the core.

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.

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].

Pyramid building stopped in Egypt long ago. When the Spanish conquered the Aztecs and Mayans, the Central American pyramids were abandoned in the jungles until archaeologists uncovered and studied them. Archaeological research continues on these structures today to resolve the many mysteries of how they were built.