Monterreal Castle is a castle in Ría de Vigo and the valley of Miñor (Val Miñor), Galicia, Spain.Construction of Monterreal Castle began in the 12th century and was completed in the 16th century, and now serves as a tourist attraction. Three of the castle's towers are preserved: the Reloj tower, the Tenaza tower with a heptagonal base and the Príncipe tower.