Three electrifying, fast, and winding descents. If you love descending, this route combines the three best trail descents in the Castejón area: Sos – Castejón, Arasán Express, and Gabás – El Rún. The route starts in Castejón de Sos and heads towards Sos up the steep slopes of the La Ribera track. At the San Andrés de Sos hermitage, with excellent panoramic views of the valley, the first descent begins on a compact, reddish rock terrain to the Castejón cemetery. From there, we first take a track and then the road that ascends to Arasán.

Opposite the Santa Bárbara de Arasán hermitage, the second descent of the route starts, the Arasán Express, a true natural bike park among oak trees that combines fast passages, narrow sections, and zigzag curves until reaching Castejón de Sos. After the ecstasy of the descent, we cross the town and catch our breath to ascend the steep slopes of the Posino track. Once in Bisaurri, we take the road to Gabás, from where the spectacular descent to El Rún starts. The trail combines technical sections (watch out for the stream crossing) with the pure essence of flow surrounded by a dreamlike forest. Finally, a comfortable track leads back to Castejón de Sos along the Ésera River.

Tetralogy Variant:

An interesting variant adds another descent to the Castejón Express trilogy to turn it into a black route. It involves taking the local route 20 upon reaching Sos, which ascends to Ramastué by track and then descends through the technical trail of the San Marcos hermitage to connect with the Castejón Express in Sos.