The Sky Pool at Embassy Gardens in London, England

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A swim in the sky

A lap in the Sky Pool may have you holding your breath, and not just because you're underwater. With the streets of London looming 10 stories down, the view through the pool's clear bottom is a bit freaky to all but the fearless. But swimming here is a one-of-a-kind experience, and for some lucky residents of these twin apartment blocks near the US Embassy, a convenient way to pop in on neighbors the next building over.

The pool is suspended 115 feet in the air, but its origin is even loftier: It was manufactured at 4,600 feet in the good ol' USA—Grand Junction, Colorado, to be precise—then shipped across the pond to its new home in sea-level London.