Senda del Oso

The Senda del Oso (Bear Trail) runs 36 km through the Trubia and Teverga valleys in south-central Asturias, following the route of a mining railway abandoned in the 1960s. The surface, paved and with gentle gradients never exceeding 3%, passes between Tuñón and the Puerto de San Lorenzo, crossing limestone gorges, iron bridges over the river Trubia and tunnels cut through rock. Converted in the late 1990s, the trail has become the most popular cycling and walking route in Asturias, with over 300,000 users per year. In the narrowest sections of the gorge, limestone walls close in to barely 10 metres apart, and the sound of water striking stones accompanies walkers for kilometres.

The trail takes its name from the historical presence of the Cantabrian brown bear (Ursus arctos) in these valleys. While spotting a wild bear requires heading into the mountains of Somiedo or Proaza with specialist guides and considerable patience, the trail offers close contact with the species at the Proaza enclosure, home to Paca and Molina, two bears rescued as cubs that could not be returned to the wild. The enclosure, managed by the Asturias Bear Foundation (FOA), is visible from the trail and has information panels on the biology and conservation of the Cantabrian bear. The estimated wild population across the Cantabrian Mountains exceeds 370 individuals (2023 census), and the Trubia and Teverga valleys form part of its western range.

The valley forks at Caranga de Abajo: the southern branch continues towards Teverga through the Foz de la Canal gorge, while the western branch climbs towards Quirós and the Valdemurio reservoir, whose turquoise waters fill the floor of a mountain cirque. Both branches maintain a cyclable surface and together total 36 km. Along the route, the villages of Tuñón, Villanueva, Proaza, Caranga and Bárzana preserve Asturian hórreos (raised stone-pillar granaries), stone manor houses with wooden galleries, and the pre-Romanesque church of Santo Adriano de Tuñón (9th century), a UNESCO World Heritage Site as part of Asturian pre-Romanesque art.

The trail suits all ages and fitness levels. The most popular section — Tuñón to Proaza, 7 km — takes roughly ninety minutes on foot or forty minutes by bicycle. Several bike-hire points (including electric bikes and child trailers) operate in Tuñón, Proaza and Teverga. The route is usable year-round, though shaded stretches may be icy in winter mornings. In autumn, beech forests on the upper valley slopes turn red and orange, contrasting with the evergreen chestnuts on the valley floor. The scent of damp leaf litter and ripe chestnuts fills the trail from October to November.

Beyond cycling and walking, the area offers complementary activities. River canoeing on the Trubia (class II–III, 8 km, April–June when water levels allow) departs near Proaza. Mountain routes from valley villages give access to summits of 1,500–2,000 metres in the neighbouring Las Ubiñas-La Mesa Natural Park. Show caving runs at Cueva de Huerta (Teverga), a 14 km cave system with stalactite formations and underground lakes. And the valley's gastronomy centres on pote asturiano, fabada, Casín cheese (PDO, hand-shaped into discs with distinctive markings) and natural cider poured in the villages' traditional chigres.