The Senda del Oso by Bike: A Practical Guide

The Senda del Oso is a roughly 36-kilometre greenway shaped like a Y, nearly flat and paved, with a shared trunk that starts at Tuñón, in Santo Adriano, and splits at Caranga toward Bárzana de Quirós and Entrago. The classic descent from Tuñón to Entrago is about 20 kilometres and takes around two hours with stops.

There was a time when coal came rattling down these valleys from Quirós and Teverga in mine wagons. Today, riding over that same rail line, is one of the best-loved greenways in Asturias: nearly flat, carved through gorges, dotted with tunnels, with a real bear waiting halfway along. It's one of those routes people set out on thinking of the kids and end up enjoying just as much themselves. This is the guide to riding it properly.

A mining railway turned cycle path

The Senda del Oso grew out of the line that carried coal out of the Quirós and Teverga coalfields toward Trubia in the early 20th century. When the mines closed, the track sat silent until it was converted into a greenway. The result is a roughly 36-kilometre network shaped like a Y: a shared trunk that starts at Tuñón (in the concejo of Santo Adriano — Asturias's term for a municipality) and climbs to Caranga, where the path splits into two branches, one toward Bárzana de Quirós and the other toward Entrago, in Teverga.

That railway heritage is its great strength. Trains hated slopes, so the gradient is minimal and constant: ride from the top ends down toward Tuñón and it's almost entirely a gentle downhill that does the work for you. The surface is paved and well kept, and the route threads through gorges and ravines, following the Trubia river between limestone walls.

The Proaza enclosure: Molina, and the memory of Paca

Around Proaza, on Monte Fernanchín, between this concejo and Santo Adriano, is the route's big draw: the cercado osero, a four-hectare fenced woodland where a brown bear lives in semi-freedom. For decades it was home to Paca and Tola, two bear cubs rescued in 1989 who became a symbol of the Cantabrian brown bear's recovery. Tola died in 2018 and Paca in April 2025; today the only resident is Molina, a female who arrived at the enclosure in 2013, barely more than a cub, after falling on the mountain and being unable to return to the wild.

Access to the viewpoint is free and it's about 700 metres from the Buyera picnic area, a ten-minute walk. Seeing her isn't guaranteed — there are no longer fixed feeding times, so it's down to luck — but early morning and late afternoon, when it cools down and she tends to be more active, are the best bets. It's worth keeping your voice down and having some patience: she's a wild animal, not a show.

The stretches, one by one

The shared trunk, from Tuñón to Caranga, is the busiest and easiest: about 11 kilometres with a gentle profile, taking in the medieval bridge at Villanueva and the bear enclosure along the way. It's the ideal stretch if you're travelling with young children or only have half a day. From there on, you have to pick a branch.

The Teverga branch, from Caranga to Entrago, adds about 9 kilometres with a few sharper climbs and runs through tunnels cut into bare rock that give the path its character — keep your phone's torch handy just in case. The Quirós branch, toward Bárzana, crosses the Valdemurio gorge through its tunnel and rewards you with mountain scenery. Many riders just do the classic descent from Tuñón to Entrago, around 20 kilometres; the keener cyclists string together the valley's long loop, around 36 kilometres.

Difficulty and plans with the family

If there's a route built for cycling with kids, this is it. The gradient is so gentle it's barely noticeable, there's no traffic, and the paved surface makes it easy going even with trailers or child seats. A good part of the route is also suitable for people with reduced mobility, especially the central stretch between Tuñón and Proaza.

The usual family formula is simple: take the hire company's van up to one of the top ends and coast back down to Tuñón or Proaza, stopping at the enclosure, at the picnic areas, and at a spot by the river to eat. The tunnels are the highlight for the kids. Budget around two hours for the classic descent, taking it easy with stops along the way.

Where to hire a bike and how it works

Several hire companies operate in the valley, mostly clustered around Tuñón, Proaza, Buyera and the top ends at Entrago and Bárzana. 2026 prices run around €28 a day for an adult bike, about €25 for a child's bike, €15 for a child seat, €25 for a trailer and around €50 for an electric bike. Almost all of them include a helmet, insurance and roadside assistance in the price.

The key part of the service is the transfer: most companies drive you and the bikes up to the top and pick you up again at the end, so you only pedal downhill. It's worth booking ahead on long weekends, summer weekends and Easter week, and confirming the return shuttle times, which vary by season. If you'd rather do the there-and-back under your own steam, that works too: the flat gradient makes it painless.

When to go and what not to forget

The greenway is good all year round, but spring and early autumn are unbeatable: fewer people, mild temperatures and the Trubia running well. In the height of summer, it's worth setting off early or heading out mid-afternoon, both because of the heat and to line up with the bear's best hours. The tunnels stay cold even in August, so a light layer never hurts.

Bring water, something to snack on, and comfortable shoes for the short walk to the viewpoint. Keep quiet at the enclosure, don't feed any animals, and take care inside the tunnels, where the light changes suddenly. With that and a clear morning, the Senda del Oso gives you one of those days you'll remember long after handing the bike back.