The Congost de Mont-Rebei Gorge is a dramatic, narrow canyon that separates the regions of Catalonia and Aragon. Hiking through the gorge takes you along a vertiginous path carved into the cliff face, offering breathtaking views over the Noguera Ribagorçana River and surrounding mountains. The hike is moderately difficult and not recommended for those with a fear of heights, but the unforgettable scenery makes the effort worth it.