World Most Amazing Places: The Pyramids and the Sphinx

A pyramid is a building where the outer surfaces are triangular and converge at a point. The base of a pyramid can be trilateral, quadrilateral, or any polygon shape, meaning that a pyramid has at least three outer surfaces (at least four faces including the base). The square pyramid, with square base and four triangular outer surfaces, is a common version.

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 distribution of weight 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, both of Egypt, the latter the only one of the Seven Wonders of the Ancient World still remaining. It is still the tallest pyramid. The largest pyramid in the world ever built, by volume, is the Great Pyramid of Cholula, in the Mexican state of Puebla. This pyramid is still being excavated.