It is situated on the southwest flank of the Mont Blanc massif, flowing from the Bionnassay Pass (3,892 m (12,769 ft) above sea level) in a generally southerly direction towards Val Veny.

[1][2] Approximately 5 km2 (1.9 sq mi) of its total area of ~11 km2 (4.2 sq mi) is covered in debris originating primarily in rockfall from surrounding walls[3] and avalanching in accumulation areas of its four tributaries.

[6] It is a popular tourist attraction due to the spectacular ice cliffs rising up to one side and its two-coloured appearance.

The colours reflect varying sediment concentrations in the water which arise as a result of the filtering effect of the debris.

[7] Huge ice blocks have been known to break off the glacier and fall into the lake, providing another major tourist attraction despite the low chance of such an event occurring.