The partly original Romanesque limestone masonry of the Staufer period of the Blue Tower in Bad Wimpfen has undergone multiple, statically relevant changes due to repeated fires and the restoration of the upper tower helmet. Since about 1851 cracks have been reported in the Romanesque masonry, which have increased considerably over time, so that at the beginning of the 1970s an extensive restoration measure with masonry injections and other static safety measures took place. In the following period, however, extensive, statically induced cracking occurred again, the causes of which have remained largely unclear. Starting in 2012, the causes of the damage were systematically investigated by an interdisciplinary team. Archive research, a fundamental examination of the existing masonry structure, various material investigations and many static model calculations of the masonry and its stresses were combined with a complex test program to form the currently implemented repair concept. An instrumented monitoring system, which has been installed since the beginning of the investigations, is used to record external influences and changes in the geometry of the tower during the repair measures and thereafter.