Mont-Dauphin dominates the valleys of the Durance and the Guil whose confluence extends under the famous stronghold. A tributary of the left bank of the Durance, the first river in Provence, the Guil waters the Queyras for 32 mi (51.5 km) and crosses eight municipalities in the Hautes-Alpes department. This torrential river has its source in the scree of the circus formed by the Pointe de Rome, the Pic Gastaldi, and the Pointe Joanne and flows into the Durance under Mont-Dauphin, in the municipality of Eygliers.