The city and municipality both rank second in population in the state. The municipality has an area of 799.9 km² (308.84 sq mi).
It is located on the country's central plateau (altiplano), 127 km (79 miles) south-east of state capital Santiago de Querétaro, at 20°23′N 99°59′W20.383°N 99.983°W and an elevation of 1,922 metres (6,306 ft). Famous for its opals, mined at nearby La Trinidad, it is also an agricultural center (corn, wheat, sugarcane, beans, alfalfa, fruit, and livestock) and has some light industry. A number of wineries are also located in the vicinity.
It is connected to Santiago de Querétaro and Mexico City by the mainline freight railway and Federal Highway 57.