Flak towers were large, above-ground, anti-aircraft gun blockhouse towers constructed by Nazi Germany.

The flak tower is a highrise reinforced concrete air defense facility built by the German Air Force during World War II as an urban air defense facility to protect strategically important cities from Allied air raids. The flak tower consisted of a G tower equipped with antiaircraft guns and a command tower called the L tower equipped with radar and antiaircraft command equipment.

The towers were operated by the Luftwaffe to defend against Allied strategic air raids against these cities during World War II. They also served as air-raid shelters for tens of thousands of local civilians.

There were 8 flak tower complexes in the cities of Berlin (3), Hamburg (2), and Vienna (3) from 1940 onwards. Other cities that used flak towers included Stuttgart and Frankfurt. Smaller single-purpose flak towers were built at key outlying German strongpoints, such as at Angers in France, Helgoland in Germany.

After the war, various equipment such as weapons were removed, and the flak tower itself was dismantled and removed, but many of them still exist and are being diverted to various purposes.

• The first generation flak tower built in Berlin in April 1941.
• It was called the zoo tower because of the place where it was built.
• Destroyed by British troops at the end of the war.
• Dimensions: 380x250x85 mm (15x9.8x3.3 inch)
• Weight: 594 g (1.31 lbs)