An air raid bunker in Berlin was constructed in reinforced concrete in 1942 during the second world war, for the German railway company. In 2003 Christain Boros bought the bunker and commissioned Realarchitektur to design a place for him and his family to live in and house his collection of contemporary art. The existing spaces seemed appropriate to be used by the art and artists represented in the collection. On each of the five floors a route connects the eight major rooms and the surrounding sub spaces.The strict symmetry and uniformity of all spaces created a general feeling of disorientation. The building was separated from its urban context by post war additions such as walls, loading bays, an elevator tower and outhouses. So austere and cold, but incredible. Since 2008 it has been opened for the public to view (by appointment only) his collection of artworks, including the likes of Damien Hirst, Tracey Emin and Sarah Lucas. Much more information about the conversion and extension here.