The river Cúa is situated in the north of the region of El Bierzo in the province of León, autonomous community of Castilla y León (Spain). It rises in the Campo de la Pesca, near the port of Cienfuegos and flows into the river Sil at Toral de los Vados. The tributaries of some importance on the right are the Ancares and Burbia rivers and of lesser volume on the left: the aforementioned Arroyo de Trayecto, the Faro river and the Biarzas river.
At first it runs in a W-E direction until one kilometre after receiving the waters of the Trayecto stream on the left, where the direction changes to N-S. It crosses the municipalities of Peranzanes, Fabero, Vega de Espinareda, Arganza, Cacabelos, Carracedelo and Villadecanes-Toral de los Vados.
