Hagen is a useful base for splitting time between the Ruhr cities and the Sauerland hills. Dortmund and Essen are 20 and 35 minutes away by train, both with major museums and the Zollverein UNESCO site at the heart of Essen. Iserlohn, with the Dechenhöhle cave system, is a 20-minute drive south.
Heading into the Sauerland, Altena Castle and the surrounding hills are about 45 minutes south by car. The cycle path along the Lenne valley starts in Hohenlimburg and follows the river deep into the hills — a good long day on a bike.