Barcelona was severely bombed by Italian and German Air Forces during Spanish Civil War, particularly in 1937 and 1938. Tunnels were used as shelters at the same time that the population undertook the building of bomb shelters under the coordination of a committee for civil defense (Catalan: "Junta de defensa passiva") providing planning and technical assistance. Hundreds of bomb shelters were built. Most of them are recorded, but only a few are well preserved. Among these stand out the "Plaça del Diamant" refuge as well as air-shelter 307 ("Refugi 307"), today one of the Barcelona City History Museum heritage sites.