The Pyramid of the Moon is the second-largest pyramid in Teotihuacan, after the Pyramid of the Sun, and located in modern-day San Martín de las Pirámides, Mexico. It is found 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.