It is an oblong lake at an alti­tude of 1,616 meters. The lake was formed in a glacial basin. The water in the lake is dark blue and flows into a drainage basin formed by the snow-capped moun­tain ranges of the Pyre­nees.

The lake’s water source is the East­ern Vali­ra and Madrid rivers. The water stored in the reser­voir is used to gen­er­ate hydro­elec­tric pow­er at a pow­er plant locat­ed near the vil­lage of Encamp.

A 6.2‑kilometer cable car leads from Encamp to the lake.