Flak towers were eight complexes of massive, above-ground, anti-aircraft concrete towers constructed by Nazi Germany as one of the answers to Allied air attacks during World War II.
After the RAF launched a successful raid on Berlin in 1940, Adolf Hitler ordered the construction of three flak towers to protect the city from aerial attacks. Berlin’s towers were constructed in only six months and, in addition, two of these massive complexes were built in Hamburg and six more in Vienna (constructed between December 1942 and January 1945).
All sixteen flak towers were designed by German architect Friedrich Tamms, had concrete walls up to 3.5 m (11 ft) thick, and were considered invulnerable to attack by RAF and USAAF heavy bombers.
It is said that Hitler himself took a personal interest in the design of the towers, and even made several sketches.
Each flak tower complex consisted of two separate towers, a G-Tower (or Combat Tower), which housed the 128 mm guns and an adjacent L-Tower (or Lead Tower), which served as the command center. The command towers also contained a retractable radar dish that could spot incoming bombers 50 miles away.
These blockhouses were equipped with at least eight 128 mm and thirty-two 20 mm guns that could fire 8,000 rounds per minute with a range of around 14 km. Each of the guns had a full 360° range of fire. These bunkers also served as civilian bomb shelters in Berlin, with room for up to 10,000 people, and even had small hospital wards.
During the assault on Berlin, the Soviets faced some difficulties in inflicting damage on the towers, even with the 203 mm (8 inch) howitzers, one of their largest guns. Special envoys had to be sent and many people in Berlin surrendered due to a lack of food and water supplies.
At the end of the Second World War, the flak towers in Berlin were destroyed by the allied forces and only two towers were preserved in Hamburg, now home to a music school and a nightclub.
All six towers in Vienna survive today. One has been transformed into an aquarium, another is used by the Austrian military, and a third as a storage facility for MAK Collection of Contemporary Art. Several projects are considered for the others.