The itinerary consists of the discovery of the viewpoint and the old marble quarry of Coll de Mu, in the municipality of Les Valls d’Aguilar. At the opencast mining operation, which was abandoned a few years ago, the Regional Council of l'Alt Urgell, through the European project Camina Pirineus, has enabled a viewpoint and installed various elements to dignify the environment and help spread the word about the geological heritage that the old quarry represents.