Kellersee, Lake in Holstein Switzerland region, Germany

Kellersee is an irregularly shaped lake between Eutin and Malente in Holstein Switzerland, about 3.2 km long and 3.7 km wide, with 555 hectares of water at 24 m above sea level and depths to 25.8 m. The Schwentine feeds and drains it. Dense reeds line much of the shore, where a wooden rowboat with a single oarsman can be seen; a roughly 16 km circular path runs partly through mixed woodland.

Kellersee lies in a moraine landscape shaped by the last ice age; its basin is unevenly formed, roughly 3.2 km long and 3.7 km wide. The Schwentine provides one inflow and the outflow, entering at Fissau in the south. In the narrow Fissau Bay, between two steep hills, the glacial relief produces dangerous katabatic winds.

The lake is managed by Fischerei Schwarten, which runs a small pub right by the shore and issues daily, weekly and monthly fishing permits to guest anglers. The excursion boat Luise offers lake tours, and the Malente sailing club uses the water. At the entrance to Malente stands Gut Rothensande, the estate that became known through the Immenhof films and now operates as a hotel focusing on equestrian sport.

This is a popular destination for anglers who can obtain fishing permits at lakeside facilities, though visitors should be aware of sudden wind conditions. The Fissau Bay area is particularly prone to unexpected strong winds that can develop rapidly.

Certain bays such as Mondschein Bay and Stille Bay freeze later than the rest of the lake, creating distinct ice patterns during winter months. These differences occur due to local water movement and the shape of the shoreline.