The largest air-raid shelters built by Germany were those beneath the gargantuan Flakturms (anti-aircraft towers) which were designed to hold perhaps 15,000 people and sometimes housed many more than this towards the end of the war. Only a handful were built, in Berlin, Hamburg and Vienna.
The tower at Heiligengeistfeld (literally Holy Ghost Field) in the Hamburg district of St Pauli is well preserved and the building is now used as offices and workshops. There is a plan to redevelop the roof of this huge structure to form a community garden and incorporate a new hotel onto the roof space.