Ciudad Universitaria (University City), Mexico, is UNAM's main campus, located in Coyoacán borough in the southern part of Mexico City. Designed by architects Mario Pani and Enrique del Moral, it encloses the Olympic Stadium, about 40 faculties and institutes, the Cultural Center, an ecological reserve, the Central Library, and a few museums. It was built during the 1950s on an ancient solidified lava bed in Coyoacán called "El Pedregal" to replace the scattered buildings in downtown Mexico City where classes were given. It was completed in 1954 at a cost of approximately $25 million. At the time of its completion it was the largest single construction project in Mexico since the Aztecs.