Pachuca de Soto (pächōˈkä ħā sōˈtō) [key], city (1990 pop. 174,013), capital of Hidalgo state, central Mexico, at the head of a ravine surrounded by foothills of the Sierra Madre Oriental. Pachuca, one of Mexico's oldest and most famous mining towns, was founded in 1534 on the site of an ancient Toltec city. The region is extremely rich in ore deposits, especially silver, which has been mined since Aztec times. Pachuca is also a cultural and educational center, with a university, a meteorological observatory, and a noted school of mining and metallurgy. In the late 20th cent. Pachuca experienced increased growth as an outlying suburb of Mexico City. Landmarks include a 16th-century convent and church and La Caja, built in 1670 as a storehouse to hold the royal tribute.