The itinerary is as follows: La Sarra – Onso Pass (Paso del Onso) – Shrine to Our Lady of the Snows (Ermita de la Virgen de las Nieves) – Ibón de Respomuso and Hut
The excursion starts at Sallent de Gállego. From there drive to La Sarra dam, about two kilometres away and leave the car in the car park at the bar/restaurant at the end of the dam, after the power station. From the dam continue by foot to the River Aguas Limpias over Las Faxas bridge. After the bridge, transfer to the GR11, which you will stay on for the duration of the excursion.
The route continues on parallel to the river, through magnificent beech woods, and crossing several ravines: the Bozitero, the Ministirio, Balsaroleta and the Garmo Negro Ravine. Once you have crossed this last ravine via a walkway, you will get to an area known as the Onso Pass (Paso delOnso), a spectacular mid-range pass that is very narrow and has drops of up to 100 metres. The River Aguas Limpias runs through the ravine. At the end of the Pass you will arrive at an extensive open area known as Llano Cheto, which ends at the Arriel Ravine. From here the climb gets significantly more difficult as you keep on the path along the river until you get to the Shrine of Our Lady of the Snows, very close to the dam on the lake. Once you have reached the Shrine, walk around the Respumoso Ibón by the right bank until you get to the hut, with its characteristic red roof.