The Pyramid of the Moon is the second largest building in Teotihuacan after the Pyramid of the Sun. The Pyramid of the Moon is located in the northern part of Teotihuacan and it mimics the contours of Cerro Gordo. Some have called it 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 A. D.
UNESCO, Nature - Misc
The Pyramid's construction between 200 and 450 A.D. completed the bilateral symmetry of the temple complex. A slope in front of the staircase gives access to the Avenue of the Dead, a platform atop the pyramid was used to conduct ceremonies in honor of Chalchiuhtlicue, the goddess of water and of the moon. This platform and the sculpture found at the pyramid's bottom are thus dedicated to Chalchiuhtlicue.