The river Segre forms the backbone of the region and provides it with its character and its shape. Around Seu - where it joins up with the Valira on its way down from Andorra - the river turns south where it must cross the Tres Ponts gorge and other geological difficulties.The four main centres are found along the river: la Seu, the area’s main town and the largest population of the Hautes-Pyrénées, is an Episcopal town with Roman roots; Organyà, the town of the Homilies, Coll de Nargó, the rafting capital of the Segre, and Oliana, the doorway to the routes to the plains. On both riverbanks, the side valleys provide the area with human richness and landscape diversity. At the Cerdanya border, around Alt Urgell in Baridà, with the municipalities of Cava, Pont de Bar and Arsèguel. Bordering to the north with Andorra, Bescaran, Arcavell, Estamariu, to the south towards the Cadí slope, with Vilanova de Banat, Alàs and Ortedó. Following the river south with the riverbank towns, the heart of l’Urgellet: Montferrer, Arfa, Adrall and el Pla. Rising towards Andorra, to the right of the Valira, the famous Sant Joan valleys which reach up to the highest part of the region: the Salòria peak. Down below, the Castellbó valley, full of stories. Towards el Pallars, the Aguilar valleys, the land of ancestral pastures.

On the other side of Tres Ponts, to the left of the Segre, appears the river Lavansa, winding course through an enclosed valley. The valley on the south face of the Cadí, with Josa, Tuixén and the towns of Lavansa, has conserved all its personality. To the south, the Alinyà valleys, a region of forests and legendary horsemen. Before Organyà, the valley of Cabó, Montanissell, Sallent, los Prats and the formidable Valldarques canyon, a fragment of Catalonia where the landscape is both beautiful and impressive, but at the same time difficult and harsh. And also Gavarra, an exceptional observation point spread out over the plain. On the gentler side of the Segre, Peramola and its inland, with pronounced, suggestive names, we find: Castell-llebre, Cortiuda, Rumbau. To the south, the lands affected by the Rialb reservoir: Basella, Castellnou and Aguilar. We also find la Clua, a survivor, upon high. Next to the Ribera Salada, Ogern and Altés route. At noon, the smooth final plains of Mirambell and Guardiola: the mountains can be made out to the north.