The Museo Fuego Nuevo (New Fire Museum) was built by architect David Peña and inaugurated in 1998. The museum is dedicated to the history of the site, especially as related by the Fuego Nuevo Codex. There is evidence of the hill's ritual use going back 4,000 years; however, the New Fire Ceremony was Aztec. Every 52 years ended one cycle and began another. The worry, however, was that the sun would not return and the ceremony was designed to ensure the sun's return in the morning. Excavation of this site and others in the borough was begun in 1974 by INAH. This work has also uncovered fossilized human and mammoth remains in neighborhoods such as Santa María Aztahuacán and Santa Marta Acatitlán.