2. Tropical Islands

Location: Krausnik, Germany
Website: tropical-islands.de

This is the largest single hall (building) in the world without any indoor support pillars. It is one of the largest buildings in the world by volume. It was built as an airship hanger but was eventually converted into an artificial tropical resort. It has a massive artificial rainforest (over 30,000 cubic-meters of soil, 500 species of plants). There's also a beach and a camping ground. We give credit where credit is due—and these guys aimed a bit higher than your average water park.