Cycle path on the dike of the Kirchhain/Ohm flood retention basin

The Kirchhain/Ohm flood retention basin (formerly also called HRB Kirchhain 3/2) of the Lahn-Ohm water association is a flood retention basin (HRB) of the Ohm in the Amöneburg Basin near Kirchhain in the Marburg-Biedenkopf district of central Hesse and belongs to the Lahn catchment area. As a "green basin" in which there is normally no water, it serves to protect the towns located on and below it from flooding (such as the somewhat distant Marburg) and it protects the Lahn river basin from flooding.
Source:
de.wikipedia.org/wiki/Hochwasserr%C3%BCckhaltebecken_Kirchhain/Ohm

The path on the dyke is closed to bicycles, even if many ride on it. At the same time there is a service road, but the view from the dyke is of course nicer.

Such a great flat path and closed to bicycles, that can't be true.