Old photos show the site at the beginning of the century: a chaotic labyrinth with some cultivated sectors, watered with promontories. Among the first systematic excavations of Leopoldo Batres (1905-1910), the decisive works of Manuel Gamio (1917-1922) and Pedro Armillas (1942-1945) and the excavation and restoration campaign began in 1962 under the direction of Ignacio Bernal, By the National Insitute of Anthropology and History and 70 years of wise efforts were necessary for Teotihuacán to begin to show its solemn geometry of its constructions and to stop guessing the strict order of amplitude of its urbanism. An artery of 45 meters wide and more than 2 kilometers of lagre represents the axis, almost exact North-South, of which the ceremonial center of the city distributes and organizes itself. The Aztecs called it the "Causeway of the Dead," because it is believed that it was surrounded by tombs, when in fact it has pyramidal platforms and each sheltered a place of worship for the gods long ago. Although the term causeway could induce an error, since it is actually a distribution of rectangular spaces in a straight line, sometimes separated by steps and others marked in the center with a symbol. A recent hypothesis indicates that some of these empty spaces could be used for the ritual "Juego de Pelota", whose absence in Teotihuacán always intrigued the investigators, until the discovery of a painting and some strange goalposts or baskets that came to show that a Variant of the sacred game was practiced, and was particular to the city.
"The Causeway of the Dead" communicates to the pyramid of the Moon, with the appropriate place for sascerdotes or cults, incorrectly called the Citadel. Between the two, to the west side of the road, rises, as a plastic evocation of the currently extinct volcanoes that are drawn on the horizon, we are talking about the famous "Pyramid of the Sun."