Bilbao (bēlbä´ō), city (1990 pop. 383,798), capital of Vizcaya prov., N Spain, in the Basque Country, on both banks of the Nervión River, near the Bay of Biscay. A leading Spanish port and commercial center since the 19th cent., it is at the heart of an important industrial area with iron mines nearby. Its banks make it a financial center. Steel, chemicals, and ships are the chief manufactures, though they have declined. Bilbao is also a center for high technology firms. It has a subway, an opera house, and several museums, including the Museum of Fine Art; the Basque Archaeological, Ethnographical, and Historical Museum; and the spectacular Guggenheim Museum (1997). Founded c.1300 on the site of an ancient settlement, Bilbao flourished because of a wool export trade in the 15th and 16th cent. In the 19th cent. it was besieged by the Carlists three times. In the Spanish civil war, Bilbao was the seat of the Basque autonomous government from 1936 until its capture (1937) by the Nationalists.