It flows through the foothills of the Eifel, and joins the Lower Rhine (left tributary).

Its origin is near Nettersheim, and its mouth in Neuss-Grimlinghausen south of the Josef Cardinal Frings Bridge.

The river is 106.6 kilometres (66.2 mi) long, which is significantly shorter than it was originally.

Due to the open-pit mining of lignite in the Hambacher Loch, the flow of the river had to be changed.

It also flows through the towns of Bad Münstereifel, Euskirchen, Bergheim, Bedburg and Grevenbroich.