Congost de Mont-Rebei in the Pre-Pyrenees of Lleida, Catalonia. Serra del Montsec, La Noguera, Lleida, Spain The Montrebei Gorge (in Catalan Congost de Mont-Rebei) is a place that is located between the provinces of Huesca and Lerida (Spain), between the regions of Ribagorza and Pallars Jussa. It is constituted in the narrowest part by which the Noguera Ribagorzana river, which constitutes the natural border between Aragon and Catalonia, crosses the Montsec mountain range, walls in vertical fall of more than 500 meters and a width at its minimum point of 20 meters. The Catalan part is part of the Noguera Nature Reserve. It is within the Sierra del Montsec Natural Interest Area.