The sky was the limit for Cargolifter AG, the German company that designed a gigantic heavy lift airship in the 1990s called the CL 160. The super-blimp was meant to carry 160 metric tons over a distance of up to 10,000 kilometers, all without the need for airports; in a natural disaster, it could carry enough food to feed over 25,000 people for two weeks, and could drop it off in an area inaccessible by conventional vehicles.

To build something that big—the CL 160 would displace over half a million cubic meters—required a big-ass hangar. So in 2000, flush with dot-com cash from an IPO, Cargolifter built a gi-normous hangar nearly a quarter of a mile in length. It's as tall as a football field is long. It's so large that if the Eiffel Tower fell over, you could drag it completely inside the hangar and not bang into anything; there are no support pillars holding up the roof, as it's a completely self-supporting dome.

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But within a couple of years, the technically-complicated CL 160 project went bust, having burned through all of the cash before it could produce the blimp. The company was out of money by 2002, and in 2003 they were forced to sell the hangar—which they'd spent €78 million to build—at an eye-watering 80% discount.

A Malaysian company snapped it up, and started doing something pretty bizarre: They spent nine months building a magnificent artificial lagoon and white-sand beach inside. They trucked in palm trees and flew a small army of Balinese craftsmen in to build a Southeast Asian village. By 2004 Tropical Islands was open for business, giving visitors access to a climate half a world away.

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For the past ten years they've continued building inside the dome, which now houses the world's largest indoor rainforest. There's a huge sauna/spa complex, a network of water slides, restaurants, shopping, guest lodges and tents you can rent for overnight stays. You can even go freaking BASE jumping inside the thing. 

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Look at the scale of this place (and if you're at work, turn your speakers up to annoy your co-workers with the catchy theme song):

The blimp that was meant to be built inside the structure never came to be, but in a supreme bit of irony, there are a couple of airships inside: Visitors can ride a tethered hot-air balloon up to the ceiling, or cruise around inside the dome in a free-floating hot-air balloon.

Here's YouTuber Tom Scott taking in the majesty: