Fuerte del Serantes is one of the best-preserved fortresses on the Basque coast, perched at 324 meters altitude on a promontory called Nueve Cruces near the summit of Monte Serantes. Built during the War of Spanish Succession under King Philip V, the fort features a distinctive pentagonal floor plan surrounded by a moat, occupying 6,800 square meters at its peak. The fortress was expanded during the late 19th century in response to emerging threats and remained garrisoned until 1918. Today it serves as an accessible historical site and hiking destination west of Santurtzi, near Bilbao.
