It is a tributary of the Duero River that starts in the Cantabrian Mountains and is 275 kilometres (171 mi) long.

[1] The most official source of the river is the “Fuente del Naranco” in Valdosín (near La Uña in León province).

They were ancestors of the modern inhabitants of Asturias and León, living on both sides of the Cantabrian Mountains.

In the 19th century, the Canal del Esla was built to irrigate the Vega de Toral.

In the 1980s, a dam and reservoir project to generate hydroelectric power required the submersion of seven villages along the Esla in León, including Riaño.