The Añisclo gorge is the least-visited of Ordesa's four main valleys, and for that alone it's worth seeking out. A narrow canyon of pale limestone drops down from the high plateau, the Rio Bellós cutting a deep slot through the rock. The path follows the river upstream through mixed forest — oak, box, and fir — with the canyon walls narrowing and widening as the terrain dictates.
The standard walk begins at the Ermita de San Urbez and follows the river to the upper canyon, about 10 km return. It is easier and less dramatic than the main Ordesa valley route but has far fewer people, especially on weekdays. The lower canyon is passable year-round; the upper reaches can be icy in winter.
From Aínsa, the Añisclo canyon is about 30 km by road via Escalona — closer than the main Ordesa valley entrance and requiring no shuttle bus. It is part of Ordesa y Monte Perdido National Park.