Baden-Baden (bäˈdən-bäˈdən) [key], city (1994 pop. 52,710), Baden-Württemberg, SW Germany, in the Black Forest. It is one of Europe's most fashionable spas; its manufactures include electronics and pharmaceuticals. The city has many parks, a large casino (built 1821–24), an opera house, and a modern and contemporary art museum. Baden-Baden was founded as a Roman garrison in the 3d cent. Its hot mineral springs were used by the Romans, and remains of Roman baths have been found in the city. It was the residence of the margraves of Baden until the early 18th cent.