A humid oasis combines recreation with exploration in a unique underwater cavern.

Possibly the most beautiful carillon in the world, set atop Iron Mountain in Florida.

Where monkeys run wild and the humans are caged.

A sprawling Baroque park with 300-year-old hydro-pneumatic waterworks.

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

Perfectly preserved ancient monastery in an impossibly dramatic location on a rocky island in the Atlantic.

Stalactites and stalagmites in a beautifully lit cave.

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

Walk 2,300 feet above the ground on the "Troll's Tongue."

These fantastically named natural pools look like something out of a Scottish myth.

Breathtakingly blue walls shimmer inside the "Glacier Behind the Town."

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

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

A beautiful geyser under environmental threat.

Centuries-old bridges grown from tangled roots.

An ethereal glowing blue ocean cave in Croatia.

Abandoned railway line circling the city of Paris.

The atmospheric road was never meant to be so creepy.

Ruins of a German Castle on top of a towering stone pillar.

An Aztec snake god has taken the material form of an apartment complex.

An island filled with hundreds of hanging, decomposing, decapitated dolls.

A battle between nature and architecture in the Cambodian jungle.

Site of a former hidden treehouse in New Orleans.

Notorious artist squat renovated into legal studios.