The Main bike path pond is an artificially created retention basin with dimensions of approx. 6 X 10 m, which is surrounded by poplars and alders. The pond is heavily eutrophicated and has an overflow that is supposed to channel collected water into the Main River. At a depth of 10-15 cm, there is a black, anaerobic layer of sludge, which is covered by extensive mats of cyanobacteria. These are mainly Oscillatoria. Numerous leaves of frogbit (Potamogeton) float on the water surface.