The Sierra de Guadarrama is a continuation of the Sierra de Gredos and provides a barrier for the province of Madrid, separating it from that of Segovia. The vegetation on the rugged slopes turns the range into a green oasis in the desert of Castilla. The streams rising here (Manzanares, Jarama) feed the province's many reservoirs, which are popular with Madrid's inhabitants (Madrileños) in summer. In winter the latter go skiing around the Navacerrada and Cotos passes.