This treasure of the Natural Park dels Ports is located in the municipality of Tortosa, near where the term limits with the Aragonese Beseit. Here, a spectacular congo caused by a long process of erosion and excavation of the waters of the captive river and contrasts with the gúbias, pools of water and incredibly smooth rocks. It emphasizes a throat of gigantic proportions, well-known like the cathedral of Els Ports, with rappel of 55m.

The majesty of the landscape is imposing and, near the course of the river, it is completed by two needles and a deep water well. The limestone rock walls make some precipices of about 600 meters high in some places.

The Gúbias del Ulldemó are flanked by some well known points by hikers and provide short, generous tours in natural pools, meanders and small waterfalls. In Tall Nou, at the confluence of the ravine of the same name and the Ulldemó river, there are fountains that sprout underground, originating surprising resurgences. If you like it, there is a circular itinerary that includes the Mola de Catí, the Cova del Rastre, the Mola Porquera, the Coll Roig, the Mas del Lino, the Enclusa, the Canal del Rito and the Tortosa or Mala fountain.