[EN] The Montes de León are located in the northwest part of the Iberian Peninsula. They extend approximately 65 km, from the Sil River (Min˜o-Sil Basin) in the west, to the Orbigo River (Douro Basin) to the east. They consist of two main alignments: the northernmost, in a north-northwest to south-south-east direction, is formed by the Aquilanos Mountains, which begin in the west in the Peñas de Ferradillo (1491 m a.s.l.) and end at Cabeza de la Yegua (2142 m), and the Teleno Mountains to the east (El Teleno, 2182 m; 42 200 4500 N, 6 230 3700 W). The southern alignment is formed by the Sierra de la Cabrera in a west-east direction, including the Pen˜a Surbia (2116 m)and Vizcodillo (2121 m) peaks. The general physiognomy of these mountains comprises two blocks of an ancient Paleozoic massif that was eroded and later raised during the Alpine orogeny. The rocks are mostly shales and quartzite from the Early Paleozoic.Cenozoic red conglomerates occupy a smaller area, appearing mainly at the foothills of the Aquilanos Mountains and the Teleno Mountains.