Six kilometers south-east of Eutin lies the Barkauer See in the middle of extensive, gentle moraines. The entrophic shallow lake is a maximum of two meters deep and around 50 hectares in size. The lake is surrounded by a belt of reeds and swamp forest, some of which is 100 meters wide. The Barkauer See is isolated from traffic and can only be reached on foot from the village of Fassensdorf.
On the initiative of NABU Eutin, it was placed under protection in 1982. Today Lake Barkau is part of the "Natura 2000" network of protected areas. The designated nature reserve has a size of 137 ha, together with the adjacent areas of the Foundation for Nature Conservation, around 300 ha are under protection. The areas bordering the lake were able to develop into semi-natural lowland moor and swamp forest. On the other areas, extensive grazing with robust cattle ensures an open pasture landscape with varied structures.