Caín is the end of the road in the most literal sense: a handful of stone houses at the bottom of the Valdeón valley where the Cares river disappears into one of the deepest gorges in Europe. From here, the famous Ruta del Cares, a footpath cut into the cliff, runs about twelve kilometres downstream to Poncebos in Asturias, hacked out of the rock in the twentieth century to maintain a water channel for a hydroelectric plant. The path clings to the gorge walls with drops of hundreds of metres, passing through tunnels and over narrow bridges, and walking even an hour of it from Caín is worth every step.
The road down to Caín from Posada de Valdeón is where you need to concentrate. It is narrow, steep and twisting, single-track in places, with stone walls, blind corners and occasionally loose gravel. Traffic comes the other way at the worst moments, including delivery vans and campers that should not be there, and in summer the parking at the bottom fills quickly. A few kilometres before Caín, the Mirador del Tombo gives a stunning view of the Central Massif, with a bronze statue of a chamois and the jagged peaks rising behind it.
The Valdeón valley itself feels remote even by the standards of the Picos. It lies in León, on the southern side of the range, cut off from the coast by the mountains and reached by roads over passes such as Pandetrave and Panderrueda. Posada de Valdeón is the main village, with a few hundred inhabitants, hotels, bars and shops. Life here was once based on cattle, sheep and goats, and the summer pastures, the majadas, are still in use. The cheese from the region, including the blue Valdeón, wrapped traditionally in sycamore leaves, is excellent and worth seeking out.
This is serious mountain country, and the weather can be harsh. Fog and rain roll in from the Atlantic, and snow can block the passes from late autumn to spring. The light in the gorge is best in the morning, before the sun moves behind the walls. Food and water are easy to find in Posada and in Caín itself, where a couple of bars serve hungry walkers.