01
1874 – 1963
The mining railway
Concession in 1874, opening in 1884. Eight decades carrying coal from Teverga and Quirós to the Trubia factory, with more than 30 tunnels dug through the rock.
From mining train to bears · Since 1874
History of the Bear Trail
The most famous greenway in Asturias was not born as a tourist route. It was born in 1884 as a mining railway. This is its full story, with real dates and companies.
See the timeline 1884 Railway opens
1963 Mining closes
1995 Greenway
1996 Bears arrive
162 years in three acts
From mining line to greenway
The most famous greenway in Asturias was not born as a tourist route. It was born as a mining railway in 1884. Here are the three acts before the detailed timeline.
02
1963 – 1990
Abandonment
Mining closed and three decades of silence followed. The route disappeared under the scrub, rails were lifted, tunnels left exposed. A forgotten scar across the landscape.
03
1995 – today
The greenway
Cyclists from Xixón pushed the reconversion. Sections opened between 1995 and 1999. Paca and Tola arrived at the enclosure in 1996. The name "Senda del Oso" took hold.
Timeline
1863 → today
162 years between the first mining-railway project and the greenway we know today. Dates and facts checked against railway sources and the Principality archives.
- 1863
mining
The Société Houllière de Quirós plans the railway
French capital looks at a Quirós–Trubia line to carry the coal out. It is not built.
- 1868
mining
The Santander y Quirós company is founded
It buys the mining rights and picks up the mining railway project toward Trubia.
- 1874
railway
Concession for the mining railway
A narrow-gauge line (750 mm) is authorised from Quirós to the factory in Trubia.
- 1884
railway
Service is inaugurated
30 tunnels dug through the rock, dozens of bridges and intermediate stations. The line starts running after ten years of construction.
- 1888
railway
The Fábrica de Mieres buys the assets
Industrial control of the Trubia basin is consolidated under a single company.
- 1892
railway
French locomotive enters service
A steam locomotive is bought in France and will run for decades.
- 1900
mining
Minas de Teverga S.A.
Company incorporated on 31 October, with 4,250,000 pesetas of capital. One of the major mining firms in the basin.
- 1912
mining
33,000 tonnes a year
244 direct workers and several departures a day. The railway is running at full capacity.
- 1940
mining
Hullasa takes over
Hulleras e Industrias S.A. is set up on 19 December and buys the operations in 1943. The railway’s last operator.
- 1963
closure
The engines fall silent
Definitive closure of the mining railway. Trains scrapped, rails lifted. The route enters three decades of abandonment.
- 1995
greenway
First greenway section
The Tuñón → Proaza section (6 km) opens in May. The reconversion begins.
- 1996
the bears
Paca and Tola at the Fernanchín enclosure
The two orphaned cubs arrive on 26 May. The route starts to be called "Senda del Oso". The Caranga → Entrago section opens that same summer.
- 1999
greenway
The Quirós branch is completed
Caranga → Valdemurio (~6 km) opens in June. The trail takes its definitive Y shape.
- 2013
the bears
Molina arrives
Molina, a rescued brown bear, joins the Fernanchín enclosure.
- 2018
the bears
Tola dies
One of the two original cubs passes away. Paca and Molina remain in the enclosure.
- 2025
the bears
Paca dies
On 10 April. Molina is left as the only bear in the enclosure, a reference point for thousands of visitors every year.
- Today
greenway
A living greenway
Tens of thousands of visitors a year — families, cyclists and photographers. The route is still intact and the 19th-century tunnels are still the same.
Background
The coal valleys
In the mid-19th century, Asturias was the most active coal basin in Spain. Coal from the Turón, Mieres, Langreo and Caudal valleys fed the iron works, the ships and the first industries. But the deposits of the Quirós and Teverga valleys had been left behind through lack of transport.
The first major attempt came in 1863, when the Société Houllière de Quirós, with French capital, planned a railway line from the pits to the arms factory of Trubia. The project was not carried out, but the idea was on the table. In 1868 the Compañía de Minas y Fundiciones de Santander y Quirós was set up, picking the project back up. The official concession came in 1874.
1824
Official concession
Narrow 750 mm gauge · Quirós → Trubia
Act one
Built with pick and dynamite
Building the route was titanic work. The line crossed two deep gorges — Peñas Juntas and Valdecerezales — which forced tunnels to be dug by pick and dynamite straight through the rock. The branch from Entrago to Perihuela alone had 18 tunnels totalling 703 m and five main bridges.
In 1884 the service was inaugurated, ten years after the concession. Track gauge was 750 mm, chosen for lower cost and tighter curve radii. In 1888, the Fábrica de Mieres bought the assets. In 1892, a steam locomotive was acquired in France that would run for decades.
1834
Service inaugurated
10 years of work · 30+ tunnels
Act two
Eighty years loaded with coal
The railway ran without interruption for nearly eight decades. The production data from 1912 — one of the well-documented years — gives a sense of the tonnage moved and the size of the workforce that operated it.
The operation passed through several companies: Santander y Quirós, the Fábrica de Mieres, the Sociedad Anónima Minas de Teverga (founded on 31 October 1900 with 4,250,000 pesetas of capital) and, finally, Hullasa (Hulleras e Industrias S.A.), set up on 19 December 1940.
Output in 1912
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0 t/year
Coal carried
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0
Direct workers
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0 mm
Track gauge
Transition
Closure and abandonment
In 1963 the steam engines fell silent. The trains were scrapped. The tunnels were left exposed, the rails lifted, the bridges unmaintained. Vegetation slowly reclaimed the route.
For three decades the old line was a forgotten scar across the Asturian landscape. Neighbours in Proaza, Teverga and Quirós remembered the trains, but nobody walked the trackbed any more: the paths were choked with ivy, thorns and occasional landslides.
"The tunnels were left exposed, the rails lifted, the bridges unmaintained."
— The line, 1963
Act three
Reborn as a greenway
The idea of recovering the route came from a group of cycling enthusiasts from Xixón. The Principality of Asturias and the Mancomunidad de los Valles del Trubia took on the project, with regional funding and, in later phases, European funds.
Every section involved clearing the tunnels, photovoltaic lighting, compacted gravel surface, bridge rehabilitation and car parks at the access points. The result is a Y-shaped greenway, with 35 km one-way, open to bikes, scooters and walkers of any age.
Section openings
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May 1995
Tuñón → Proaza · 6 km
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Summer 1996
Caranga → Entrago · 14 km
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June 1999
Caranga → Valdemurio · Quirós branch
Why it is called this
Paca and Tola arrive
While section 2 of the trail was about to open to the public in the summer of 1996, on 26 May 1996 two orphaned Cantabrian brown bear cubs entered the Fernanchín enclosure, a semi-wild facility set up by FOA (Fundación Oso de Asturias) between Proaza and Santo Adriano.
The cubs had originally been named Selva and Charli. Following their arrival at the enclosure and the media coverage, they were renamed Paca and Tola. The name "Senda del Oso" took off commercially after the bears arrived.
Tola died in 2018. Paca died on 10 April 2025. Today Molina remains, a brown bear rescued in 2013 who lives in the same enclosure. Her full story is at /senda-del-oso/paca-y-tola/.
1946
Paca and Tola arrive
26 May · Fernanchín enclosure
What remains today
The trace under your wheels
Riding or walking the trail, the mining legacy is everywhere if you know where to look. The 30-plus tunnels are the same ones 19th-century workers dug. The bridges keep their original structure. Several intermediate stations have been turned into rest areas with information panels.
For anyone who enjoys industrial heritage, the Bear Trail (Senda del Oso) is one of the best examples of repurposed mining railways in Spain, along with the Vía Verde del Pas (Cantabria) and the Vía Verde de la Sierra (Cádiz).
What survives
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+0
Original tunnels
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0 km
Operating greenway
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0
Years of history
Ride through the history
The best way to live it is by pedalling
All of this is there, under your wheels or your feet, waiting. Riding the 22 km downhill of the Teverga branch in two or three hours with a stop at each point of interest is the most complete way to discover the trail.