The Sierra de Guara is among the great limestone landscapes of Spain, and the Mascún gorge, cut deep into its southern flank, is one of the best known. The river has worn a long, narrow canyon, with walls hundreds of metres high, and at its head stands the little village of Rodellar, which has become a pilgrimage place for climbers from across Europe. Mascún III lies about fifteen kilometres from Alquézar and farther still from any big town, and it is one of a series of painted shelters in the canyon. They carry figures in the Levantine tradition, protected by UNESCO as part of the rock art of the Mediterranean basin in Spain. Another ride connects it to the beech woods of the Hayedos de Navarra, which tells you how far these routes travel.
The land is a mixture of bare crags, holm oak, box and pine, with the Guara's highest point, just over two thousand metres, often with snow in winter. The canyons are full of birds, including griffon vultures, which soar over the rim in the afternoon, and at dusk, bats pour out of the cliffs. In the pools of the Mascún, canyoners in wetsuits drop from ledge to ledge, a sight that gives the place a restless, cheerful energy in summer.
The ride in is a real adventure, narrow, twisty and rewarding. Roads wind through isolated villages in tight bends, with sharp climbs and sudden drops into gullies. They are largely empty, but surfaces can be rough, patched and gravelly, and the last section to the canyon is the sort of road where you slow down without being told. Be careful after rain and in winter, when ice can linger on shaded bends. Spring and autumn are the best seasons, and midsummer can be hot, though evenings are cool.
Angüés and Boltaña are small, so plan to fill up in Huesca, which has more than fifty thousand people, or in Barbastro, before you head into the mountains. Rodellar has a small bar and a campsite, but do not count on anything else. Carry water, food, and a warm layer.