At Carcassonne in the Pyrénées its course is oriented north-south. The Aude then presents the characteristics of a mountain stream as it traverses Capcir and feeds several reservoirs (Matemale, Puyvalador) before plunging into gorges (those of Saint-Georges are the most scenic) crossing ancient terrain. Starting from Axat, after being joined by the "Aiguette" on the right bank and the "Rébenty" on the left bank, the river flows through bands of pre-Pyrénéen limestone (in the Pierre-Lys Gorges) and passes through a series of small communes: Quillan, Espéraza, Couiza, Alet-les-Bains, then Limoux. Downstream of this great medieval city, the Aude flows eastwards. This elbow results from a Stream capture, the Aude having once flowed in the valley of the Hers, indicating a deepening by an ancient hydrology following the uplifting of the Pyrénées.