An exceedingly ambitious mega-structure proposed for Tokyo, Sky Mile Tower, which, as the name suggests, would stand a mile tall, was conceived in 2016 by US architecture firm Kohn Pedersen Fox.

The 420-story eco-skyscraper would feature everything from floating farms to feed its 55,000 inhabitants to technology that could harvest water from clouds. However, the chances of it ever being built are very slim indeed.

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