The landscape in northern Brandenburg offers lakes with crystal-clear water surrounded by forest. More than 100 of these lakes are located in the Stechlin-Ruppiner Land Nature Park. Lake Stechlin, east of Rheinsberg, is 69 metres deep and one of the best explored lakes in Germany. It is surrounded by large, partly swampy forests that shield it from the influences of modern agriculture. This means that hardly any liquid manure or fertilisers get into the lake. The extensive forests are also a perfect retreat for otters, beavers and the extremely rare European pond turtle.