The maars and crater lakes were formed more than ten thousand years ago by small, local eruptions of volcanic gases.
In marsh regions of the Westerwald large fish ponds were laid out for centuries which today resemble natural lakes.
In the narrow valleys of the Hunsrück reservoirs were created by building dams in order to ensure the water supply, even outside of the mountains e.g. for the city of Trier.
In the northwestern part of the Upper Rhine Plain, which belongs to Rhineland-Palatinate, there are no natural lakes.
In addition, small streams were impounded to create bathing lakes, supplementing the normal swimming pools.