The Mont-rebei Gorge (El Pallars Jussà - La Noguera - Spain) natural space covers a surface area of about 600 hectares. It was purchased by the Territory and Landscape Foundation of the Caixa Catalunya Friendly Society in 1999 with the aim of preserving its natural and landscape values. For the most part it is included within the natural interest space (PEIN) of the Montsec and it also borders on the Partial Nature Reserve of the Mont-rebei Gorge. In 14 Apri 2005, the Mont-Rebei Canyon has been declared a Wildlife Refuge.

The Mont-rebei gorge, created by the river Noguera Ribagorçana as it passes through the Montsec mountains,separating the Montsec d'Ares from the Montsec de l'Estall and is the only great gorge in Catalonia (Spain) which has been kept more or less intact without being crossed by any road, railway or electricity line. It is only crossed by a mule track partially dug out of the rock, allowing this spot to be enjoyed in a very spectacular manner. The walls of the gorge reach vertical heights in excess of 500 metres at points where the minimum width of the gorge is no more than 20 metres.