Reservoir of Pedrezuela Nature · Guadalix de la Sierra, Cuenca Alta del Manzanares, Madrid Closed off in 1967 across the River Guadalix, it flooded pastures, drovers' roads and the old Tres Ojos bridge, as well as the original sanctuary of the Virgen del Espinar; its sheet of water completely transformed the landscape of the eastern comarca. Photo: Calima (CC BY-SA 3.0) What to see and do in Guadalix de la Sierra