This reservoir, built in 1972, is the largest reservoir in the Community of Madrid with an area of 1,070 hectares and a capacity of 426 cubic hectometers, being the main responsible for the water supply of the city of Madrid. It is flanked by the towns of El Atazar (which gives it its name), El Berrueco, Cervera de Buitrago, Patones, Puentes Viejas and Robledillo de la Jara (http://www.embalsedelatazar.es/). Its walls dam the waters of the Lozoya River and these contain good populations of trout, barbel, vogue, pike and black bass that can be fished throughout the year if we have the current fishing license from the Community of Madrid. Although some of its banks are easily accessible, others, however, require long movements by the fisherman on foot through terrain, sometimes quite steep, creating natural areas where fish have barely seen lures or baits.