A brightly colored natural bridge formed by mineral-rich hot springs high up in the Andes.

This magnificent stepwell is designed as an inverted temple and adorned with 1,500 sculptures.

This whimsical statue dumps water on its head to symbolize knowledge flowing into his brain. Or maybe booze.

The world's largest indoor go-kart racetrack is hiding in Connecticut.

19th-century scientists would make the pilgrimage here to verify the precision of their measuring sticks.

Six ravens are kept captive (but well-fed) at the Tower of London to prevent the fall of the Crown.

A public display of prehistoric space rocks is named for the Namibian village where they were found.

A remote horde of architectural treasures fit for Indiana Jones.

A giant concrete Brutalist water tower in suburban Johannesburg.

A domed disco abandoned since the '70s now attracts artists and explorers under its unique roof.

A creepy sculpture of a decapitated head invites viewers to see St. Louis through its empty eyes.

Things aren't quite what they seem at this mind-bending museum.

This striking icon of the disputed Republic of Artsakh caused a stir at a Eurovision Song Contest.

Though technically an illegal structure, this eclectic DIY apartment complex is beloved by its residents.

Step inside the first house designed by Catalan architect Antoni Gaudí, considered to be one of the first Art Nouveau buildings.

The vertical-axis windmills of ancient Persia have been grinding flour for 1,000 years and counting.

Football field-sized microalgae production tanks on the Hawaiian coast create a stunning view from space.

The antique hotel still has a jail in the basement, though the cockfighting ring is long gone.

Exquisite wall sculptures carved in secret by an early quarryman in an obscure corner of the Paris Catacombs.

Beautiful antiques and obscure engineering artifacts trace the evolution of phones from rare luxuries to ubiquitous.

The sculpture is made of more than 100,000 knives collected to raise awareness about violence.

A tower-like theater in the Swiss Alps built to withstand the high winds and avalanches of the mountain pass.

A tribute to an iconic act of defiance from the Croatian War of Independence involving a small car.

The Virginia home of one of the signers of the Declaration of Independence is being preserved with a unique glass facade.