The blockhouse towers – enormous concrete and steel leviathans that dominated the skyline – were constructed in Berlin, Hamburg, and Vienna and used in defense against Allied air raids. Each one was built over the course of just six months, however they’re remarkably durable and feature three and a half meter-thick walls that served as air-raid shelters and sites the Luftwaffe used to defend the cities.
Today, Vienna’s Haus des Meeres could not be further displaced from this reality. Located in Esterhazy Park, the site offers views over the city, and the interior offers five floors of displays. A multi-story greenhouse has been constructed on the outside of the flak tower, complete with wooden walkways and rope bridges, and tropical vegetation that thrives amid small water features.
Inside, fish and turtles are on display while a variety of tropical birds and marmosets wander freely among the visitors. The Haus des Meeres also has a vivarium where visitors can find snakes, lizards, and crocodiles, and even a shark aquarium on the ground floor.