Traunsee, Lake, Upper Austria, alt. 423 m, area 24,5 km2, Lake Traunsee is 12 km long, 3 km wide, and 191 m deep; it is the second largest lake in the Salzkammergut region and deepest lake in Austria (the largest lake in the Salzkammergut is Lake Attersee ). It has good water quality and, because of its great depth, a low water temperature. The lake is situated in a transitional zone between the Alpine foreland and the Alps between the Hoellengebirge mountains to the southwest, Roetelstein mountain (1,287 m, Roetelseen Underground Lakes) and the Traunstein mountain (1,691 m) in the east. The River Traun flows through Lake Traunsee. Holiday resorts on shores of the lake are in the north, west and south: Gmunden (spa, alt. 440 m), Altmuenster (alt. 442 m), Mitterndorf (alt. 441 m), Traunkirchen (alt. 443 m) and Ebensee (alt. 443 m). The steep eastern bank is less densely populated. On a small island close to Gmunden lies the castle Schloss Ort, where the Gmunden summer festival takes place; Lake Traunsee offers all kinds of watersports.