A historic natural way of passage from Provence to Piedmont and the former Kingdom of Savoy, the Guil crosses the entire territory of the Queyras valley and hosts the main access road to this region on its banks. It has its source in the Mont Viso circus where rainwater and snowmelt run off the slopes of nearby peaks over 9,842 ft (3,000 m), i.e, the peaks of Marte, Venice, Udine, Rome, Gastaldi, Joanne as well as Mont Ruine, Asti, and Mont Aiguillette. They first feed the three lakes of the Viso circus (Lestio, Porcierole, and Clot Sablé), then combine to form the Guil torrent and descend into the valley.