The gorge of Montrebei is a huge crack in the river Noguera Ribagorzana dug in the middle of the Sierra del Montsec thousands of years ago. It forms the natural border between Aragon and Catalonia and the walls of the canyon can reach over 300 meters of vertical drop points where the minimum width of the gorge is only 20 meters.

It is a gorge that offers a spectacular landscapeintact and away from the hand of man, with the singularity of its walking trails enclaved in the rock. It is located along the river Noguera Ribagorzana, between the town of Puente de Montañana and Canelles reservoir.