Each valley has a number of marked walking trails, which you can find out about at the park’s Centro de Interpretación and on its website.
One of Somiedo’s best (and most popular) walking areas is the Valle de Lago, whose upper reaches contain glacial lakes and high summer pastures. Here the Ruta de Valle de Lago (6km, around 2½ hours one way) trail leads to Asturias’ most expansive lake. You must leave vehicles in Valle de Lago village.
Other good walks include the La Peral–Villar de Vildas route in the upper Pigüeña valley (13km, around five hours one way), which passes one of the largest and best-preserved brañas, La Pornacal; and the challenging ascent of El Cornón (2194m), the park’s highest peak (14km, around nine hours return).
Heading east from Somiedo towards the Senda del Oso, you'll find more good hiking opportunities at the Puerto de San Lorenzo, a 1347m pass where the the road crosses the Camín Real de la Mesa (GR101), an ancient track linking Astorga (Castilla y León) with the Asturian coast.