The base of the climb is Pla de Senarta (1.375 m), see "Getting There" in the MAIN PAGE for getting there.
From the municipal camping of Pla de Senarta (1.375 m) take the forest trail to the right and into the wood. There is a barrier in the begining. The trail, wich is named GR (Gran Recorrido) 11, surrounds the slopes of Obago de Vallibierna and then goes in parallel with Río de Vallibierna. Pass some gorges on the slope of Pico d'Estatás, leave Cabaña del Quillón (1.785 m - 1 h 30 min) up and to the left, and reach an area with many water sources. The forest trail ends in the wood of Llosas, cross Puente de Coronas and leave Refugio de Coronas (1.990 m - 2h 30 min) to the right. Cross some meadows along the river and, before starting an ascent to Pleta de Llosas (there're some falls), turn to the right (S) crossing at least two streams (3 h 05 min. They join to Río de Vallibierna in the meadows below. Start a long and hard ascent to the left of Canal de Vallibierna frst, cross the stream at about 2.300 m, go in parallel with Barranco de Culebras leaving it to the left and reach Collado de Culebras (2.789 m). Turn to the left and climb Tuca de Culebras (3.062 m - 6 h 40 min), there are pitches of grade II . Descent to the arête called Paso del Caballo, cross by siting on it or grabing the edge with your hands and putting the feet on some little slabs on the W face (left). Climb on an easy ridge to Vallibierna (3.067 m - 6 h 55 min).
Take crampons, ice axe, rope, harness, warm clothes and good mountaineering boots in winter. Don't forget compass and map, and take an altimeter if possible in any season. Bring enough water in August because some little streams could be dry. In summer take a shell jacket because there use to be storms in the afternoons.
If attempting in a day, start early in the morning and never underrate the climbing pithces, they could be easy but the cliffs are very deep in many cases. The surrounding of Refugio de Coronas or the meadow below the steep slope to Collado de Culebras are good places for passing the night