Dam of the Barrios de Luna reservoir Monument · Los Barrios de Luna, La Montaña de Luna, León Image of Los Barrios de Luna, not of the place itself. Concrete gravity dam 80 metres high and with a capacity of 308 cubic hectometres, designed by the engineer Luis de Llanos y Silvela between 1935 and 1936 and built from the summer of 1945 despite opposition from the valley's residents. The gates were closed for the first filling on 15 June 1951, and sixteen villages and hamlets, among them Arévalo, Láncara de Luna and Mirantes de Luna, were submerged beneath its waters. Franco officially inaugurated it in 1956 to irrigate the Páramo Leonés and the Órbigo district, a river formed by the union of the Luna and the Omaña. It is crossed by the AP-66 motorway over the Ingeniero Carlos Fernández Casado cable-stayed bridge, the one with the longest span in Spain after that of the Constitution of 1812 in Cádiz. Photo: Fotosventana (CC BY-SA 3.0) What to see and do in Los Barrios de Luna