A pyramid is any three-dimensional structure where the upper surfaces are triangular and converge on one point. The base of pyramids are usually quadrilateral or trilateral (but generally may be of any polygon shape), meaning that a pyramid usually has three or four sides. The measurements of these triangles uniformly classify the shape as isosceles and sometimes equilateral.
A pyramid's design, with the majority of the weight closer to the ground, means that less material higher up on the pyramid will be pushing down from above. This allowed early civilizations to create stable monumental structures. For thousands of years, the largest structures on Earth were pyramids: first the Red Pyramid in the Dashur Necropolis and then the Great Pyramid of Khufu, the only remaining Wonder of the World. The largest pyramid ever built, by volume, is the Great Pyramid of Cholula, in the Mexican state of Puebla. This pyramid is considered the largest monument ever constructed anywhere in the world, and is still being excavated. Although the name pyramid is used across the world to describe ancient structures convention dictates that naming them such is not really correct. Technically a true pyramid has four smooth sides and the only ones that exist are those in Egypt and various other areas around the world which were based on the Egyptian model.
The most famous pyramids are the Egyptian pyramids — huge structures built of brick or stone, some of which are among the largest man-made constructions. Pyramids functioned as tombs for pharaohs. In Ancient Egypt, a pyramid was referred to as mer, literally "place of ascendance." The Great Pyramid of Giza is the largest in Egypt and one of the largest in the world. Until Lincoln Cathedral was built in 1300, it was the tallest building in the world. The base is over 13 acres in area. It is one of the Seven Wonders of the World, and the only one of the seven to survive into modern times. The Ancient Egyptians capped the peaks of their pyramids with gold and covered their faces with polished white limestone, though many of the stones used for the purpose have fallen or have been removed for other structures over the millennia.
Most Egyptians prepared for death; they tried to provide a secure resting place that would last an eternity. Although this was their wish, it did not work that way. Often the weather and tomb robbers were the main culprits that destroyed many tombs. Most tomb robbers, who were believed to be the tomb builders, often reentered the tomb after it was sealed, unwrapping the mummy and removing all amulets and stones. The coffins made of wood, which also held many precious stones, were also picked and destroyed. After destroying the tomb, many of the mummies would be taken out and burnt for fuel or sold as a souvenir product. Although tomb robbers were the main culprits, modern cultures also influenced the desecration of many mummies.