The Tonsee near Pätz is an old Tonkute, which explains the name of the small headland in which clay was mined until 1945.
The lake is not of natural origin. Rather, it came into being at the end of the 19th century when numerous brickworks were built in the region. This was also the case in 1895 when the Heise & Schrobsdorff brickworks mined clay near Pätz to produce bricks. It is said from 1910 that 25 million bricks were produced there every year. Due to an uncontrolled inflow of water, a connection road to Prieros broke off in 1927 and partially sank into the lake. Workers built a new section of road around 100 m further north, which in the 21st century will be part of the B 246. During the Nazi era, there was a vehicle depot for the Schutzstaffel on the west and south banks from 1943 to 1945. In 1944 and 1945, when the clay was mined, workers exposed a strong water vein that could no longer be closed. The clay pit was abandoned and filled with groundwater. The brickworks including the kilns were demolished in 1953. During the GDR era, the SS buildings that had become vacant were initially used by the Free German Youth and later by the GDR border troops. The lake was used for breeding pikeperch. It is still there in 2018. There are also pike, perch, carp, eel and tench.
Source: Wikipedia