The Torre del Oro, or Gold Tower, is a military watchtower in Seville, built by the Almohad dynasty to control access to Seville via the Guadalquivir river. Built in the early 13th century, the tower served as a prison during the Middle Ages and as a secure enclosure for the protection of precious metals periodically brought by the fleet of the Indies, another possible origin for the tower's name. Nowadays, the restored tower is a naval museum, containing engravings, letters, models, instruments, and historic documents.