Teotihuacan, the birthplace of the gods, lies roughly 50 km northeast of Mexico City. Built between the first and seventh centuries A.D., it is notable for the enormous grandeur of its monuments, particularly the Temple of Quetzalcoatl and the Pyramids of the Sun and Moon, which are laid out on geometric and symbolic principles. Teotihuacan is Mesoamerica's most prominent cultural center. The area was occupied by 400 B.C., but it was not until 3 centuries later that it witnessed large-scale urban expansion, thanks to refugees from Cuicuilco, a city devastated by volcanic activity. The first surveys were conducted out in 1864, and the excavations began in 1884 by discoverer, Leopoldo Batres. The city was founded in 400 B.C., developed to become the most prominent and influential city in the region by 400 A.D., when it was designated a UNESCO World Heritage Site in 1987.