Flakturm - papermodel 1/144

Flak towers (German: Flaktürme) were 8 complexes of large, above-ground, anti-aircraft gun blockhouse towers constructed in the cities of Berlin (3), Hamburg (2), and Vienna (3) from 1940 onwards. Other cities that used flak towers included Stuttgart and Frankfurt (Main).
They were used by the Luftwaffe to defend against Allied air raids on these cities during World War II. They also served as air-raid shelters for tens of thousands of people and to coordinate air defence.

The most of german airports has smaller Flak towers too, standing on each corner of the airports and defending them against air-raids of fighter and fighter-bomber and of course bomber.

From Wikipedia, the free encyclopedia / foto from http://www.vintagewings.ca