The entrance to this natural wonder is under the vertical walls of Monte Mondarruego, the source of the Ara River and its tributary, the Arazas, which forms the famous Ordesa Valley. Defined by the Ara and Arazas rivers, the Ordesa Valley is endowed with pine, fir, larch, beech, and poplar forests; lakes, waterfalls, and high mountain meadows. Protected wildlife includes trout, boar, chamois, and the sarrio or isard (Rupicapra pyrenaica) mountain goat.
Well-marked mountain trails lead to waterfalls, caves, and spectacular observation points. The standard tour, a full day's hike (eight hours), runs from the parking area in the Pradera de Ordesa, 8 km (5 miles) northeast of Torla, up the Arazas River, past the gradas de Soaso (Soaso risers—a natural stairway of waterfalls) to the cola de caballo (horse's tail), a lovely fan of falling water at the head of the Cirque de Cotatuero, a sort of natural amphitheater. There is one refuge, Refugio Gorez, north of the
cola de caballo. A return walk on the south side of the valley, past the Cabaña de los Cazadores (hunters' hut), offers a breathtaking view followed by a two-hour descent back to the parking area. A few spots, although not technically difficult, may seem precarious. Information and guidebooks are available at the booth on your way into the park at Pradera de Ordesa. The best time to come is May to mid-November, but check conditions with the tourist office, Centro de Visitantes de Torla, before risking driving into a blizzard in May or missing out on el veranillo de San Martín ("Indian summer") in fall.