Rivulet Fehla, the second half of its way of 15,5km is through a Naturschutzgebiet. From its karst spring at Burladingen it meanders through a peaceful valley, whose terrain is totally without roads; there is only a sandpath for pedestrians and bicycle drivers. The rivulet joins the Lauchert at Hettingen. The lower part of the Fehla runs through a deeply karstic area, where some water sinks into the underground to rise up again 13km southwest in the strong karst spring “Gallusquelle”. The small spraying steps in the water is accumulated, chemically precipitated limestone.