Tropical Islands Resort is a tropical water park located in the former Brand-Briesen Airfield in Halbe, a municipality in the district of Dahme-Spreewald in Brandenburg, Germany, 31 miles from the southern boundary of Berlin. It is housed in a former airship hangar (known as the Aerium), the biggest free-standing hall in the world. Inside the hall, the air temperature is 79 °F and air humidity is around 64%. Tropical Islands is home to the biggest indoor rainforest in the world, a beach, many tropical plants and a number of swimming pools, bars and restaurants.

Source: Wikipedia