This unique temple complex remains off the typical tourist trail.

Barcelona's historic 19th-century sewers, whose foundations were laid in medieval times, are open to the public for exploring.

This centuries-old Italian chapel hangs midway down a sheer cliffside.

This Oregon farm is dedicated to teaching people the professional art of tree climbing.

The tallest outdoor elevator in Europe rockets passengers on a dizzyingly precarious ride to the top of a mountain.

Space-age monument to an early 20th-century uprising.

A quick and simple solution to Cambodia's train woes.

A decommissioned submarine base makes a great space for graffiti art.

The longest continuous lava tube in Oregon.

Two planes stand abandoned after the closure of an aircraft-themed restaurant.

This enchanting natural park is a magical example of a temperate rainforest in Europe.

A spring-fed pool so deep it's used for scuba diving as well as swimming.

An emerald-green grotto just a short trip from Austin.

Get up close and personal with these majestic fish.

Walking through this narrow gorge will make you feel like you've fallen into a fairytale landscape.

The idyllic island where the philosopher Jean-Jacques Rousseau spent “the happiest time of his life.”

Men in rubber-soled boots serve as your "brakes" on this toboggan ride Hemingway described as "exhilarating."

At night, bats patrol this magnificent 18th-century space in search of book-eating pests.

The haunting beauty of this little-visited wreck makes it a true hidden treasure.

Wondrous stalactites house thousands of bats in these African caves.

Daily jousts and dancing barrel makers in Munich's mechanical clock.

A trail weaves through the verses of a poem illustrated by stone sculptures inspired by Native American pictographs.

Hidden behind West Philadelphia rowhomes is a haven for migratory and local bird species both ordinary and rare.

Get past the gatekeeper's apartment and enter an elaborate hoax of a restaurant with a Masonic feel.