I thought I add a short comment to the non-German speaking community. If your are interested in climbing and want to experience an extraordinary spot- this is the place to go.
The Landschaftspark Nord is an old Thyssen Steel mill and the former Bunker area has been transfermed into a climbing arena that is second to none. Raw concrete left to its natural decay. So while the securing bolts are checked, the rest of the routes changes over time. It is fun to visit again and again.
Prices are low (if you are checked at all) and the are is open at all times. So even climbing at night is possible. However the routes with a ceiling are limited - so when its raining, climbing is too. In this case, just walk around the park. It is an experience by itself.
If you want to go there and have no car - take the tram 903 from Duisburg main station and step of at Landschaftspark Nord - Then it is a short walk (15-20mins) and you are there. Check Google maps for details. read more