Attersee, also known as Kammersee, English sometimes Lake Atter, is the largest lake of the Salzkammergut region in the Austrian state of Upper Austria. It is Austria's third largest lake by area, surpassed only by Lake Constance and Lake Neusiedl, which, however, both extend beyond national borders.The surface area extends for about 20 km (12 mi) from north to south and 4 km (2.5 mi) from east to west. With an average depth of 85 m (279 ft), its water volume even surpasses the Chiemsee, which is larger by area. The main inflow is the Seeache creek, which flows out of the nearby Mondsee lake in the southwest. Both Attersee and Mondsee are part of a chain of lakes, beginning with Fuschlsee and Irrsee. The waters flow off with the Ager River down to the Traun which itself discharges into the Danube at Linz.