Castle of Borriol Monument · Borriol, La Plana Alta, Castellón The castle of Borriol, a ruined medieval Arab fortress that dominates the village from a hill to the north of the settlement, occupies, in the Plana Alta comarca, the site where in Roman times a watchtower may have stood, visually linked to other nearby watchtowers to guard the Vía Augusta. The present fortress, of Muslim layout profoundly reformed by later Christian constructions, is organised on three levels: the upper level preserves towers, a cistern and remains of walls and auxiliary structures; the middle level was modified in the 19th century to adapt it as a military garrison; and the lower level corresponds to the wall defending the access path. It has been declared Bien de Interés Cultural (Spain's highest level of heritage protection) since 25 June 1985. Photo: Falconaumanni (CC BY-SA 3.0) What to see and do in Borriol