Ten stories tall, the building is covered in its entirety by mosaic stone murals depicting the history of Mexico. The building was built by architects Gustavo Saavedra and Juan Martínez de Velasco, and the murals conceived and executed by artist and architect, Juan O´Gorman. Began in 1948, the building took four years to complete and the stone mosaic murals cover 4,000 square meters. Amazingly all of the stones (even the bright blues) are in their natural colors, O´Gorman travelled all across Mexico to find the perfect stones. He chose to use natural occurring colors because painting the stones would have required constant renovating and re-painting. In the state of Guerrero they found the yellow, red, black and green stones. Some of the green stones were also found in the state of Guanajuato, and in Hidalgo they found volcanic rock that was in the hues of purple and pink. The blue was the hardest to find, but they finally found the blue stones in a mine in Zacatecas. The Central Library (La Biblioteca Central) is located in the north part of University City (Ciudad Universitaria), about a block east of Insurgentes, and two blocks south of Universidad.