River Nalón Nature Trail (Fuso - Tuñón)

The route begins at Fuso de la Reina, next to the FEVE (Ferrocarriles Españoles de Vía Estrecha) railway station, and runs parallel to the railway tracks until it leaves the town behind. Immediately after, it continues parallel to a hydroelectric canal fed by the Nalón until it reaches an intersection. Here, the route veers right onto a level crossing. It then continues parallel to the railway line until it slowly drifts away from the tracks and the water canal towards a metal footbridge across the river. Numerous wetland bird species, such as mallards (Anas platyrhynchos), grey herons (Ardea cinerea), common moorhens (Gallinula chloropus), and grey wagtails (Motacilla cinerea) can be seen, and, with a little luck, even an otter (Lutra lutra).

The Trail runs along the right bank of the Nalón, immersed in a well-developed riparian forest, mainly populated by alders (Alnus glutinosa), black poplars (Populus sp.) and ashes (Fraxinus sp..). Past a junction, the route continues along the left bank until it reaches a bridge with views of the peculiar Priorio castle. After passing under a bridge over the Nalón, it heads down the road to Caces.

At the entrance of the town, next to a playground, the route turns right and traverses through a few streets with fine examples of traditional architecture, including several "hórreos" (granaries) still in use. The route continues straight ahead at the first intersection, then veers right at the next two junctions and continues along a dirt road that links with a paved road that runs alongside the Nalón.

With no room for confusion, the paved road winds down parallel to the river through a lush area populated with chestnut trees (Castanea sativa), between meadows and fields, including a kiwi farm that exports tons of fruits to Europe. Further on, the path reaches the junction with the road leading up to Pintoria, from where it continues to the right, always parallel to the river, towards Trubia.

The path stumbles again onto the railway tracks, and, immediately after, reaches the industrial facilities of Química del Nalón, located on the outskirts of Trubia. Once in town, it runs through its streets towards the train station, where the Trail can cross the tracks either via a metal footbridge or at the level crossing. It continues through the town centre towards the River Trubia, at the edge of the town.

The route follows the right bank of the river, leaving behind several bridges, past various industrial facilities, to reach the intersection with the road to Perlín. It now veers right to the church of Santa María de Trubia, where the Trail turns left behind an abandoned farmhouse. From here to San Andrés, the Trail traverses meadows, croplands and a lush mixed forest dominated by maples (Acer sp.), ashes and chestnuts.

In San Andrés, the route ventures onto a path to the left, parallel to the road, which leads to an old quarry with a wooden footbridge over the road and the River Trubia, then continues left along a paved road.

The path then winds along the floor of Trubia Valley, moving towards the limestone walls of Peña de la Escalera and the slopes of La Recusa and Las Garradas. It then traverses the old railway tunnel, and continues up the valley while slowly approaching the River Trubia. The route crosses a metal bridge over the river and reaches Tuñón recreation area, next to AS-228, where this Nature Trail ends and one of the sections of the Bear Trail begins.