It is born in Fuente del Infierno (Leon), in the valley of Sajambre. It arrives at Asturian lands through the pass of The Beyos, council to Ponga.

The voice Sella proceeds of the indo-european one Salia, and is utilized to name a course of water, a current, a river.

The total course of the Sella is of 73 Km, its basin has a surface of 1.200 Km2 and the medium volume is of 34 m3/sg, with maximums in December and April. It elapses for 5 Asturian municipalities and 1 leones.

The rivers Ponga, Dobra, Güeña and Piloña are its main affluent.