How the Germans are reusing these invincible Nazi towers

During World War II, Hitler personally ordered the construction of massive, steel-plated towers that bristled with anti-aircraft guns, tearing planes from the sky like King Kong on angel dust. For modern Germans, these nearly indestructible towers provide a unique problem: They don't want to waste well-engineered buildings and materials, but they're not super into maintaining relics of Nazi triumph.

So the Germans have found interesting ways to re-purpose the old fortresses.

​A German flak tower under construction in 1942 as part of Germany's defenses against Allied bombing raids. Some of the expensive towers have been re-purposed in the decades since the end of the war.

(German Military Archives)

The strategy of constructing the towers was questionable to begin with. It required massive amounts of concrete and steel for the walls that, in some cases, are over two feet thick. Construction in Berlin was completed in six months and additional towers were built in Vienna and Hamburg before Germany was defeated. Construction took so much material that rail shipments had to be rearranged around them, slowing the flow of needed materiel and troops to battlefields and factories.

Just the Zoo Tower in Berlin required 78,000 tons of gravel, 35,000 tons of cement, and 9,200 tons of steel. The towers were built in pairs. For each primary tower devoted to anti-aircraft operations there was a second tower that had some anti-aircraft weapons, but also sported communications and other support equipment.

But the towers, once completed, were nearly impregnable. They relied on no single support pillar, and nearly every structural support was so strong that they were almost impossible to destroy from outside. When Germany was conquered, Soviet forces who took Berlin had to lay siege out of range and negotiate a surrender of the towers.

But there was one major shortfall to the towers. They were designed to stop air raids on Berlin, and it was dangerous to attack the city within range of the towers. So, planes simply flew outside of their range or approached them en mass, fielding so many planes that the Germans simply couldn't get all of them at once.

German soldiers man a flak gun on a tower in World War II. The massive towers were a significant obstruction to air raids on three German cities, but were part of a questionable military strategy.

(German Military Archives)

Plus, Germany lacked proximity fuses during the war, meaning their flak weapons were less effective than those used by the Allies — at least, when the Allies were willing to use the fuses and risk their capture.

After the towers finally surrendered, engineers worked to destroy them, but quickly found that massive amounts of explosives were needed and, even then, many would still stand. The Zoo Tower, mentioned above, survived two attempts at destruction. The first attempt used 25 tons of explosives and the building shrugged it off.

The third attempt, powered by 35 tons of dynamite, finally did the job.

Outside of Berlin, some of the towers survived destruction attempts while a few were simply left in place. Instead of destroying them, locals decided to re-purpose them over the years.

At first, Germans simply stripped the towers of valuable materials and left the steel-reinforced buildings in place. But, over the years, the brilliant German engineers found ways to make use of buildings with excellent thermal insulation and structural integrity.

A storehouse for art in Vienna, Germany.

(Photo by Bwag)

In Vienna, one of the six towers is now an aquarium maintained by the Aqua Terra Zoo. Visitors can see over 10,000 fish and other aquatic organisms in the tower. On the outside of the tower, visitors can use the climbing wall that has been added.

Another Vienna tower has been turned into an antenna for cellular phones, and one is used to store art in controlled conditions.

In Hamburg, two towers have been re-purposed. One holds nightclubs and businesses and the other provides energy storage for part of the city.

Solar collectors cover the tower and work with butane and wood burners to heat large water tanks inside the tower. The thick concrete walls provide insulation and the water is pumped to nearby buildings, heating them during the cold months. The tower is also used to generate electricity for 1,000 homes.

While most of the towers in Berlin were destroyed to one degree or another, in one case, the rubble was simply covered over with dirt, forming two hills in a public park for visitors to sit on.

Check out the YouTube video below from Real Engineering to learn more.