Herdecke is a town in the district of Ennepe-Ruhr-Kreis, North Rhine-Westphalia in Germany. It is located south of Dortmund in the Ruhr Area. Its location between the two Ruhr reservoirs Hengsteysee and Harkortsee has earned it the nickname Die Stadt zwischen den Ruhrseen (lit. The city between the Ruhr lakes). The city is located in the area of the Regionalverband Ruhr (RVR). The two Ruhr lakes as well as the forests on the Ardey heights make the town attractive to tourists. The historic center with its many half timbered houses and the 30 metre high railway viaduct across the Ruhr valley are two more landmarks.