In an exquisite location on the banks of the Rhine, where it commands an impressive view, the "Rheintower" residential tower in the Mühlheim district of Cologne sets new standards for outstanding urban housing: 21 floors, a height of 76 metres, 102 rental apartments with a total area of approx. 7260 square metres – these are the key figures for a high-rise building that is exceptional in many respects.

The architects commissioned to design the facade, kister scheithauer gross architects and urban planners (ksg), who have offices in Cologne and Leipzig, developed a facade design, under the direction of Prof. Johannes Kister, that defies convention and creates a distinctive identity at the same time: curved balconies and numerous rounded features give the building a vibrant, sculptural appearance that varies significantly according to the angle of view and emphasises the sophisticated complexity of the building envelope. The clinker brick slips designed and manufactured specifically for the project, through close collaboration between the clinker specialist Ströher and ksg, constitute the successful realisation of an idea to provide the high-rise building with an opalescent outer shell. At the same time, the brick slips – which are expressly designed not to mimic a solid brick wall, but to proudly stand for what they are – emphasise the imposing curves of the building.

Prof. Johannes Kister explains the basic idea behind his facade concept in terms of the choice of materials and the unconventional and complex laying arrangement: "The black brick slips are installed vertically to follow the curves of the floor plan and they feature embossed grooves that reflect light onto the dark clinker surface. The horizontal joints are offset and create the impression of a swirl that climbs up the building in a spiral. Light and its reflections are a significant design element that give the building plasticity and movement." 

According to Prof. Johannes Kister, this explains why the "Opal" residential tower can claim its own high-quality individual identity: "A high-rise building not only needs an effective floor plan, but also a design in the third dimension, from the base to the top. Opal's curves and protruding balconies create an interplay, a coherent unity that can and should be observed from every angle".