Vía Verde de la Sierra de la Demanda, Railway trail in Sierra de la Demanda, Spain.

The Vía Verde de la Sierra de la Demanda is a 52 km greenway between Arlanzón and Monterrubio de la Demanda, built on the 1901 narrow-gauge mining railway of The Sierra Company Limited. It runs through pine, oak and beech woods and past the Arlanzón reservoir. Of its three tunnels, only the one at km 40 is open; the tunnels at km 10 and km 31 (Manquillo) are closed, and detours climb steep tracks.

This route traces an abandoned mining railway that once carried minerals from the Sierra de la Demanda mines to industrial centers in northern Spain. When mining operations ceased, the railway was transformed into a recreational trail.

Pineda de la Sierra, at kilometre 23, is listed as a historic-artistic complex, with mountain-style houses and a Romanesque church with a portico. Barbadillo de Herreros, at kilometre 44, keeps a furnace and other remains of its old ironworks. The hamlet of Bezares is today a single agricultural holding.

The route runs 52 km from Arlanzón to Monterrubio de la Demanda, with the only station of the old line at Arlanzón. Two tunnels, at km 10 and km 31, are closed by collapses or poor condition and are bypassed by steep tracks; the hardest point is the climb over the Manquillo pass. The tunnel at km 40 is the only one open. Maintenance is difficult for the six municipalities that share the route.

The railway's construction uncovered the Atapuerca archaeological sites, now a World Heritage Site since 2000. There is talk of extending the greenway from Arlanzón to these sites. The route also passes the former village of Bezares, today a single dairy farm.