The Ciudadela is a monumental structure in Mesoamerica that is composed of 15 pyramids and encompasses approximately 11 areas. Mesoamerican pyramids form a prominent part of ancient Mesoamerican architecture. Although similar in some ways to Egyptian pyramids, these New World structures have flat tops (many with temples on the top) and stairs ascending their faces. The largest pyramid in the world by volume is the Great Pyramid of Cholula, in the east-central Mexican state of Puebla. The builders of certain classic Mesoamerican pyramids have decorated them copiously with stories about the Hero Twins, the feathered serpent Quetzalcoatl, Mesoamerican creation myths, ritualistic sacrifice, etc. written in the form of hieroglyphs on the rises of the steps of the pyramids, on the walls, and on the sculptures contained within.