Valley of la Barranca Nature · Navacerrada, Cuenca del Guadarrama, Madrid A mountain valley at the foot of the Bola del Mundo, 2,265 metres, and La Maliciosa, 2,227 metres, in the Sierra de Guadarrama, within the municipalities of Navacerrada and Becerril de la Sierra. It is crossed by the río Samburiel, a tributary of the Manzanares, held back in two small dams before flowing into the Navacerrada reservoir, and by an extensive Scots pine forest whose most characteristic botanical feature is bearberry, scarce elsewhere in the sierra. Next to the first dam stand the ruins of the old Santo Ángel tuberculosis hospital. The climb up La Maliciosa, with an elevation gain of almost a thousand metres, is one of the best-known mountain routes, and its north faces offer climbing routes for experienced climbers. Photo: Miguel303xm (CC BY-SA 2.5) What to see and do in Navacerrada