The Fortification can be visited
Town FortificationDuisburg
Duisburg Town Fortification

In the area of Duisburg's old town, remnants of the historic city wall with individual towers can still be discovered. It is considered one of the oldest in the Rhineland; its existence dates back to the 12th century. A complete impression of the defensive structure can be gained from Johannes Corputius' city map (1566).
Image: http://www.wehrbauten.de/thread.php?threadid=564
Location: 51.4379, 6.7646