Today, the flak tower in Volkspark Humboldthain is for many people an observation deck, but during the Second World War the building was part of the city’s fortifications.

The flak tower is third of three flak towers built in Berlin from 1940 to 1942 at the idea of Hitler himself.

The idea was that the flak towers, with their 40-meter-high corner towers, would protect the city center from Allied air raids. FLAK is short for Flugabwehr-Kanone or anti-aircraft canon.

The four corners of the flak towers were the gun towers. Up there stood the heavy artillery. A 128 millimeter caliber double flak cannon that could shoot 15 to 20 kilometers away. On the plateau below, lighter flak cannons were placed. These were quadruple guns with 20 millimeter caliber projectiles designed for close combat.

Inside, the flak towers were built with five floors, the two upper floors for military personnel and the three lower floors for civil protection, accommodating around 10,000 people. The flak towers thus also served as bunkers, and with their 2.5 to almost 4 meter thick walls and ceilings, the bunkers were the most secure air raid shelters for the berliners.

As bunkers, they were so bomb proof that even though Soviet troops shelled the flak towers constantly with their tanks in the last few weeks of the war, the artillery could not penetrate the walls.

The flak tower in Humboldthain also shows clear signs of tank fire – in some places with holes half a meter deep in the walls.

The flak tower in Humboldthain is the only one remaining in Berlin – and only as a ruin – as they were all blown up as part of the demilitarization of Germany after the war.

Click here to find the locations of the flak towers

The French army was in charge of destroying the flak tower in Humboldthain, but as it is located right next to the railroad, which was partly administered by the Soviet occupying forces, only half of the bunker was blown up. If the railroad was damaged in the blast, the French troops risked a diplomatic crisis with the Soviets.

The French army, on the other hand, imagined that the collapse of the south side of the flak tower would take the rest of the bunker with it. However, this didn’t happen, so the northern side is still exposed and you can climb the many steps and use the gun tower as an observation deck.

Berliner Unterwelten offers guided tours inside the ruins. You can find out more about the tour on the Berliner Unterwelten website.

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