The Mascún gorge is one of the great pieces of rock in the Sierra de Guara, a canyon with walls that rise several hundred metres, and it is the reason the village of Rodellar has become a pilgrimage site for climbers. Mascún I is a small shelter on the high ground above, in a district of cliffs, pines and thin soil, and it belongs to the Mediterranean-arc rock art that UNESCO listed in 1998. I can tell you that you will not have to share the view with a crowd. This is one of the emptiest corners of the Pyrenean foothills.
The road to it is slow. From Huesca the main way is long and winding, through oak woods and across ridges, with narrow sections and a few unpaved spurs. Plan on more time than the map suggests. Surfaces are patched, rockfall is possible after heavy rain, and in winter the upper stretches can ice up. The reward is solitude, with griffon vultures turning on the thermals and big skies of the kind you rarely get in northern Europe. A bearded vulture or an eagle is a real possibility.
Do not count on fuel. Alquézar is fifteen kilometres away and has a few hundred inhabitants, Angüés and Boltaña are small, and the nearest big town in the data is Huesca, over thirty kilometres off. Fill up in Huesca or Barbastro, carry water and some food, and tell someone your route if you head onto the unpaved sections. The nearest village bar might be closed on a weekday afternoon.
In summer the canyon has a cool micro-climate, and the cliffs act like a storage heater in the evening, so a night near Rodellar is warm and the sky is full of stars. Spring is the best season, when the hills are green and the stream runs. Autumn is also fine, though the days are short. If you walk to the viewpoint over the gorge, take a hat, because there is no shade, and listen for the sound of rope on rock far below.