The Sieg is a 146 km long, low mountain range river, whose source is in the Rothaar Mountains and which crosses into the Rhine-Sieg district near Windeck-Au. 70 kilometres downstream, the Sieg flows into the Rhine near Niederkassel-Mondorf.
Due to its outstanding abundance of rare plants and animals, the Sieg in the Rhine-Sieg district is one of the most beautiful and most ecologically important stretches of river in Germany. The Siegaue area, from the state boundary at Windeck-Oppersau to the point where the river joins the Rhine, was thus designated a conservation area in 2005.
In order to preserve the beauty and uniqueness of the flora, fauna and landscape along the Sieg, special rules apply to visiting the Siegaue and to canoeing on the river. More information on this is available at www.rhein-sieg-kreis.de.