Dock of the Canal de Castilla Monument · Alar del Rey, La Ojeda, Palencia The Canal de Castilla is one of the most important works of hydraulic engineering built in Spain between the mid-18th century and the first third of the 19th, conceived to give Castilian wheat an outlet to the northern ports before the railway made it obsolete. Its northern branch begins at Alar del Rey, a village that did not exist before the canal and that grew up as the central hub of the works; founded in 1657 by royal will, it has as its patron San Luis Rey de Francia, in honour of the French engineers who directed the works. The canal basin at Alar del Rey, considered a unique example in Spain of 18th-century industrial architecture, is the infrastructure that gave rise to the village and its purpose; the whole has been declared a Bien de Interés Cultural (Spain's highest level of heritage protection) as a historic-artistic ensemble since 1991. Photo: Valdavia (CC BY-SA 3.0) What to see and do in Alar del Rey