The Caves of Monte Castillo, located in the Cantabrian town of Puente Viesgo, contain one of the most important Paleolithic sites in the region. The complex of karstic caves is on the slopes of Monte Castillo, a hill south of Puente Viesgo, with an elevation of 354 m. It includes four out of the eighteen caves listed as World Heritage of UNESCO since July 2008 under the title of Cave of Altamira and Paleolithic Cave Art of Northern Spain: El Castillo, Las Chimeneas, and La Pasiega and Las Monedas. In addition, the complex includes a minor fifth cave, La Flecha. The caves are located along the Pas river in the Castillo mountain, squarely at the intersection of three valleys and near the coast.