In reply to UKC Articles:
The b&w photo was taken in 1945 after an unsuccessful attempt by the occupying powers to blow it up after the end of the War. Berlin was ringed by these flak towers, as were other major German cities, a legacy of the huge air defence system built to counter the relentless bombing by RAF Bomber Command by night and the USAAF by day. The resources poured into air defence were huge amounting to the equivelent of numerous divisions in terms of man power and guns, particularly 88 mm guns, which were sorely needed on the Eastern Front and which some historians believe coud well have tipped the balance in favour of the Axis.
The fact that demoliton proved so difficult, impossible in the case of this one, shows just how strong re-inforced concrete construction is.