Nazi Flak tower. Used against allied aircraft in Europe. They had an air defense range of 14km and could put up 8,000 rounds in a minute!!!
Berlin WW2 German flak tower - there were three of these giants in Berlin,the Soviet tank guns could not dent them. They held thousands of Berliners and were surrendered at war's end.
10 Abandoned Gun Emplacements, Artillery Batteries and Flak Towers
Flak Tower Hamburg - well served its purpose, better to hid....
WWII Flak tower, Vienna. When I saw the size of this in the early 80s I couldn't believe what it was and it wasnt mentioned in the guide books at that time.
Re-purposed World War Two Flak Towers | Urban Ghosts
Flak tower - Wikipedia, the free encyclopedia
WW2 Bunkers-The Subject Of Contemporary Controversies And Urban Conversions - http://www.295luv.com/home-design/ww2-bunkers-the-subject-of-contemporary-controversies-and-urban-conversions.html
Zoo Flak Tower in Berlin after being bombed by Allied Planes, 1940s Imgur World War Two