The Nidda is a right tributary of the Main river in Hesse.It springs from the Vogelsberg on the Taufstein mountain range near the town of Schotten, flows through the Niddastausee dam, and the towns of Nidda, Niddatal, Karben, and Bad Vilbel. At Harheim it reaches the Frankfurt am Main city area and after 98 km enters the Main in Frankfurt's Höchst quarter.In the 1920s and 1960s, the flow of the Nidda was regulated to reduce the risk of floods.