ALMADÉN, or Almadén del Azogue, a town of Spain, in the province of Ciudad Real; situated in mountainous country 55 m. W.S.W. of the city of Ciudad Real. Pop. (1900) 7375. Almaden, the Sisapon of the Romans, is celebrated for its mercury mines, which were extensively wrought by the Romans and Moors, and are still productive, the ore increasing in richness with the depth of the descent. The mines ranked with those of Adria, in South Austria, as the most valuable in the world, until the great development of the mercury deposits at New Almaden, in California, U.S.A., between 1853 and 1857. They were long worked by convict labour, owing to their unhealthy atmosphere; and exemption from military service is granted to miners who have worked at Almadén for two years. The annual yield is about 1,400,000 lb. Lead and sulphur are obtained in the neighbourhood. The nearest railway station is that of Chillén, 3 m. S. on the Madrid-Badajoz-Lisbon line.