California's own majestic geyser is powered by a subterranean volcano.

Don't blink or you'll miss it.

Inside an old airplane hangar, friends and strangers alike play on a massive trampoline.

The giant pair of sexy legs sticking out the window of this costume store have become its main draw.

This lovely little bridge hidden in a Switzerland gorge is essentially a fairytale.

Hundreds of stone stairs and a winding medieval bridge connect this haunting Spanish island to the mainland.

Every equinox this Maya pyramid puts on a spooky ancient light show.

An experimental, automotive replica of Stonehenge.

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

The Denver airport is guarded by a 32-foot-tall sculpture of a demonic horse.

A still functioning vaudeville carousel that has operated for over a century boasts a colorful menagerie and past.

This concrete tangle of square pipes has stood as a proud thorn in the city's side since the '70s.

The world's largest mountain carving could fit all of Mount Rushmore inside it many times over.

This charming colonial alleyway is one of the oldest continuously used residential streets in the U.S.

When ecosystems collide in the arid Southwest.

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

A nondescript building that's been functioning as a speakeasy for nearly a century and a half.

Catacombs turned marketplace.

A shop full of natural curiosities, carnivorous plants, and costumed taxidermied mice.

This cemetery has graves dating back to the 17th century, including the city's oldest carved tombstone and an ominous cryptogram.

Eighty million natural history specimens call this gargantuan museum home.

San Francisco's newly reopened hands-on science museum.

A 400-year-old mummified arm dangles from the ceiling of St. James the Greater, serving as a warning to thieves.

An existential riddle in the world's largest ancient castle.