Conversion of a WWII air raid bunker into the residence of an art collector. The listed air raid bunker was constructed during the second world war and was originally based on plans of the architect Karl Bonatz. The building could house up to 3000 seated people distributed on five floors during air raids. The inner spatial structure has an axially symmetrical layout, that is surrounded by a 1,8 meter thick outer concrete wall and a 3 meter thick concrete ceiling. In the year 2003 an art collector bought the bunker and commissioned Jens Casper and his office at the time Realarchitektur to design a place for him and his family to live in and house his collection. Outer additions were removed, the facades were cleaned and have been structurally refurbished. Selected ceilings and walls were cut out of the building, the resulting overlapping spaces now join the floors vertically throughout. Only parts of the interior walls are plastered and painted white. Traces of all former uses and incidents, graffiti, scars, bullet holes remain present. To connect up to the newly created dwelling on top of the building, around 150 cubic metres of concrete were cut out of the bunker roof. The apartment is reached through this opening by way of a steel staircase and an internal open lift. It is laid out as an open plan with the living spaces flowing through the entire area. It has a ceiling height of 3.75 meters. Only few materials were used for the interior: concrete, smoked oak and shell limestone. The apartment is surrounded by a load bearing steel-glass facade, gardens, terraces, a pool and the Berlin roofscape.
The project has been widely published and received many prestigious awards such as Deutscher Architekturpreis Beton 2008, the contract.world award 2009, The Chicago Atheneum Awards 2009, and a BDA Preis Berlin 2009.