Torrelavega, city, Cantabria provincia (province), in the Cantabria comunidad autónoma (autonomous community), northern Spain. It lies southwest of Santander city, at the confluence of the Besaya and Saja rivers. Founded in the 14th century, the city owes its name to the Garcilaso de la Vega family, notable in medieval times. The city is an industrial and rail communications centre, and its livestock fair is one of the most famous in Spain. Manufactures include chemicals (dyes and sulfuric acid), plastics, and synthetic fibres. Iron, lead, and zinc mines are in the surrounding region. The cave of Altamira, famous for its prehistoric paintings, is in the vicinity. Altamira was designated a UNESCO World Heritage site in 1985. Pop. (2007 est.) mun., 55,418.