Flakturm

Flaktürme, or flak towers, were large, fortified anti-aircraft gun towers constructed by Nazi Germany during World War II to defend key cities such as Berlin, Hamburg, and Vienna from Allied air raids. Built of reinforced concrete, they housed heavy flak guns (typically 88mm or larger), radar equipment, and command centers. Some towers also served as air-raid shelters, accommodating thousands of civilians. Designed to resist bombing, they featured thick walls and multiple levels. Their height and firepower provided effective air defense, though they were difficult to destroy. Several flak towers still exist today due to their massive construction.