Evan Lake, in the Province of Qazvin, is situated in the historic Alamout area, home to the world-famous Alamout fortress, which was once the headquarters of the Ismaili sect, led by Hassan Sabbah between the 11th and 13th centuries.

The lake has a surface of 70 square kilometers (27 square miles) at 1,800 meters (5,905 feet) above sea levels. The Avan Lake is crystal clear and is solely supplied by underground spring discharges. Fishing, swimming and sailing are the activities available during summer. In autumn it hosts migratory birds such as swan, goose and duck. The lakes surface freezes in winter and is suitable for ice-skating.

The lake is located at an altitude of 1,800 meters above sea-level, with a maximum length of 325 meters and a width of 275 meters. The deepest section of the lake is 7.5 meters and extends over 70,000 square meters. Avan Lake is fed by rainwater and the ever-gushing springs that supply very clean and transparent water. The only tributary that flows into the lake is named Ovan, which streams down from the northern mountains. The north of the lake is also surrounded by three small villages: Varbon, Avan and Zarabad.

The excess water of the lake overflows to form a small river that irrigates farmlands in the villages of Kushk and Ain. Most residents of these two villages either breed livestock or work their land.