mountain chain generally extending along the northern coast of Spain for approximately 180 miles (300 km). Scenic and well forested (with beeches and maritime pines), the mountains are of geologically similar origin to the Pyrenees, though classified as a separate formation. They comprise a series of high ridges rising inland from Torrelavega, in Cantabria and Palencia provinces, and crossing (east-west) Asturias and northern León toward Galicia. Fractures have sharply demarcated the range from the Castilian plateau (part of the Meseta Central) in the south and the Cantabrian coastlands in the north, but the eastern and western limits are indistinct. The eastern foothills south of Cantabria rise abruptly into the gigantic limestone mountains of the Europa Peaks, which include Torrecerredo (8,688 feet 【2,648 metres】) and the Labra Peak (6,620 feet 【2,018 metres】). The main ridge continues westward, usually less than 60 miles (100 km) wide but with elevations of 5,000 to 7,000 feet (1,500 to 2,000 metres). Most of the higher peaks—including Vieja, Prieta, Llambrión, Naranjo de Bulnes, and Espigüete—exceed 8,000 feet (2,500 metres) and are along the main ridge. West of the Narcea River valley, the ranges change their east-west trend and the Sierra de Rañadoiro runs almost north-south. The main ridge divides into the Sierra de Ancares and the Sierra del Caurel, to the northwest, and the Sierra de Gistreo and the León Mountains, to enclose the basin of El Bierzo, which is drained by the upper Sil River.

These chains are a more impressive barrier than the Pyrenees. The Oviedo-León railway crosses the Pajares Pass at 4,524 feet (1,379 metres) and is one of the most difficult railway passes in Europe. Heavy river currents run northward from the mountains, forging deep valleys, while to the south the mountain's longer rivers are used for irrigation. The region is economically important because of its iron and coal deposits and as a source of hydroelectric power for the coastal region. Cattle raising is still the dominant economic activity, however. Tourism in the area has increased in importance.