In the page's words:

A special gem for contemporary art and culture from Germany and abroad - this is the significance of the more than 800-year-old Zündorf fortified tower today. It is located on the Groov leisure island, one of the most attractive excursion destinations in Cologne on the right bank of the Rhine and is not only one of Zündorf's most striking landmarks, but also a unique exhibition venue. Used for residential and defensive purposes in the Middle Ages, the tower has a special architectural feature in store for visitors: The modern interior construction made of exposed concrete, which was hung into the medieval "shell" by Cologne architecture legend Gottfried Böhm at the end of the 1970s.

Further information at: zuendorfer-wehrturm.de