Aguascalientes, city (1990 pop. 455,234), capital of Aguascalientes state, central Mexico. The city is a pleasant health resort, noted for its mineral waters and vineyards. Its industries include railroad repair and the manufacture of textiles. Aguascalientes is built over an ancient, intricate system of tunnels constructed by early, still unidentified, inhabitants. Founded in 1575, the city was long a Spanish outpost; railroad development in the late 19th cent. gave it commercial importance.