Castro Urdiales is the largest coastal town in Cantabria after Santander. It was one of the most important fishing villages and ports in the Cantabrian Sea since the Middle Ages.
The medieval town is located at the foot of the rock or walled fort that was reinforced in the early years of the Middle ages. There are interesting ruins of a Romanesque hermitage, a medieval bridge and the opportunity to have a good meal of fresh fish in a restaurant in the port.