The Pyramid of the Moon is the second largest pyramid in modern-day San Juan Teotihuacán, Mexico, after the Pyramid of the Sun. It is located in the western part of the ancient city of Teotihuacan and mimics the contours of the mountain Cerro Gordo, just north of the site. Cerro Gordo may have been called Tenan, which in Nahuatl, means "mother or protective stone." The Pyramid of the Moon covers a structure older than the Pyramid of the Sun which existed prior to 200 AD.
The Pyramid's construction between 100 and 450 AD completed the bilateral symmetry of the temple complex. The pyramid is located at the end of the Avenue of the Dead, connected by a staircase, and was used as a stage for performing ritual sacrifices of animals and humans upon. It was also a burial ground for sacrificial victims. These burials were done in order to legitimize the addition of another pyramid layer over the existing one. The passing of several rulers, and rapid changes in ideologies, led to the Pyramid of the Moon's exponential expansion between 250 and 400 AD.