The mountain bases are located between 900 and 1,200 metres above sea level, and the principal peaks of the range have an average topographic prominence of 1,000 metres. The range's highest peak, Peñalara, reaches 2,428 metres above sea level. The range begins in the valley of the Alberche river, which divides the Sierra de Gredos into two portions, and finishes at the Somosierra Pass, which serves as the hydrographic boundary between the river basins of the Tagus and Douro rivers. The mountains contribute fluvial material to both rivers through the action of various mountain streams, such as the Jarama, Guadarrama, and Manzanares, which empty into the Tagus, and the Duratón, Cega, and Eresma, which flow into the Duero. The geographical coordinates of the range's northeast terminus lies near 41° 4' North, 3° 44' West, and the southwestern end near 40° 22' North, 4° 18' West.