San Pedro hill Nature · Colmenar Viejo, Cuenca Alta del Manzanares, Madrid An isolated hill 1,425 metres high in the sierra de Guadarrama, between the municipalities of Colmenar Viejo, Guadalix de la Sierra and Pedrezuela. Owing to its character as an island mountain, separated from the main range of the sierra, it offers a very wide viewpoint: to the north and west the Cuerda Larga and the sierra de la Morcuera can be seen, and to the south, the skyline of Madrid. In summer its sparse vegetation gives it a characteristic yellowish colour. It is of pre-Hercynian origin, formed mainly of gneiss, whose erosion has enriched the soils of the dehesa of Navalvillar, a protected area on its southern slope. Only the M-625 road, between Colmenar Viejo and Guadalix, crosses it. On its summit there once stood a chapel dedicated to Saint Peter. Photo: Sixto Emmanuel Picones (CC BY-SA 4.0) What to see and do in Colmenar Viejo