Five buildings lined up along the Rhine – this is Mainz’s new residential quarter, Zollhafen. Each one is different, but a shared visual identity and location on the same plateau ensure their unity. The plateau’s topography creates a unique identity for each building vis-à-vis the street, with inviting staircases and uniquely tailored accessibility features enabling barrier-free access to the plateau via ramps and stairs. These features define the intersection between the public street and the private garden areas that are shared among residents. On the side facing the Rhine, the plateau establishes a clear division between its private gardens and the public loop.

Who lives directly on the banks of the Rhine? Everyone! At least everyone who belongs to the 'Five Friends. Each apartment’s living spaces and balconies enjoy an ideal orientation toward the river. Exhibited in this way, the river in turn inspires the five buildings’ appearance. The material and colors of the cranes that are central to the logistical operations of the harbor are reflected in the colorful steel of the facades and the balconies projecting from the buildings. The Zollhafen, or customs port, with its docks, high quay walls for fluctuating Rhine water levels, and industrial relics such as cranes, ladders, and bollards, is a remarkable and unusual environment for residential structures.

The 'Five Friends' are consciously recognizable as apartment buildings, enjoying the natural beauty of the Rhine via large windows and suspended open spaces. At the same time, they echo the themes of their industrial surroundings through their facades of coated profile sheeting, front-facing steel grids, and color schemes. In the summer, forward-facing verandas provide shade for the apartments, while in the winter the low sun provides warmth. Solar gains are invited into the building through movable exterior sun shades. Green retention roofs and facade plantings cool and improve the microclimate outside the buildings, while materials like clay construction panels do the same inside.