archaeological site in northwestern New Mexico, U.S., on the Animas River, just north of the city of Aztec. The national monument was established in 1923 and has an area of 0.5 square mile (1.3 square km). The site, mistakenly called Aztec by early white settlers, actually contains the excavated ruins of a 12th-century Pueblo Indian town built of masonry and timber. Many Indian artifacts are displayed at the visitor centre. The monument was designated a World Heritage Site in 1987.