The Abbey of Saint-Martin-du-Canigou sits at 1,094 metres on a narrow rocky spur above the Cady river valley, about an hour's walk from Vernet-les-Bains. The path up is well-marked but steep; there is a Jeep service from Casteil at the bottom if you prefer. The abbey itself is one of the finest examples of early Romanesque architecture in the Pyrenees, its simple stone church and cloisters dating (in origin at least) to the early 11th century.
The setting is spectacular — the abbey appears to grow directly out of the cliff, with vertical rock above it and a long drop to the valley below. Guided tours run several times daily and are the only way to see the interior. The monks still live here; the community is welcoming but asks visitors to respect the religious nature of the site. On a clear day, views extend east toward the plain of Roussillon and the Mediterranean.