The largest Bohemian glacial lake (18,4 ha), the deepest (40m) in the Šumava mountains, part of a Nature Reserve (since 1911), at an elebation of 1008 m. Above in the 320 m high Lake Rock (Jezerní stěna), an outstanding view point. The first re-pump water-works in our country were built in the valley below the dam in 1929-30.