The principal rivers are the Fier, which travels through the Bornes whose source is at Lake Annecy, and the Chéran, sourced from the Bauges. The Fier leaves the Albanais to the west via a water gap at Val-de-Fier, at an opening between the Princes Mountains and Gros Foug, from there she enters the Rhone downstream from Seyssel. The outlet of Chéran in the Albanais at Allèves, Semnoz and Mont Bange. The Sierroz, a short intermittent mountain stream, also runs into Lac du Bourget. These turbulent rivers carved out of the Albanais sandstone narrow gorges deep.