A former reservoir that was only recently discovered after more than 60 years of disuse.

Denmark’s never-ending bridge.

A lonely beacon, precariously perched atop a remote sliver of rock.

This eccentrically decorated palace is replete with grottoes, fountains, tunnels, and caves.

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

This rock formation named for its unique shape is one of many that call the Alabama Hills home.

The world's greatest slide descends 18 stories from this looping mountaintop viewing platform.

Rainforest filled with record-holding eucalyptus.

Dolphins, ancient clams and hundreds of waterfalls make this one of the world's top tourist destinations.

The only Bahá'í house of worship in North America and one of only a handful worldwide.

This punny mirror of another Wisconsin attraction is exactly what it sounds like.

This elaborate Hindu temple is located in a Chicago suburb, but looks like it was transported directly from India.

A dangling church built over a Colombian gorge.

A monument to the art of slicing people open.

In the middle of an extremely unforgiving and desolate high desert is the most secret military facility in the world.

A Hawaiian stairway to heaven—that you can't climb.

Centuries-old bridges grown from tangled roots.

Hellam Township is reputed to feature seven remote gates, which when passed through in the right order, open an entrance to hell.

Keshwa chaca, among the last handwoven Incan bridges, crosses Apurimac Canyon in Peru.

One of the tallest buildings in Iceland, and perhaps, the most visually impressive.

A gargantuan crystal kingdom.

The longest continuous lava tube in the continental U.S. offers 2.5 miles of dark explorations for the adventurous.

The deepest lake in the United States, and once the site of epic destruction that lives on in legends.

Once the most densely populated place in the world, this island is now a ghost town.