These caves are home to a small church and were used to age cheese.

Perhaps the most spectacular grotto along the Algarve coastline.

These curious caverns have been home to mushrooms, gangsters, and disco.

Off-limits and full of venomous pit vipers, Brazil’s Snake Island has a frighteningly apt nickname.

A preserved section of the Atlantic Forest is an important habitat for these critically endangered monkeys.

This unique bird reserve sits within an important fragment of Brazil's Atlantic rainforest.

This Irish show cave is said to have been the site of a Viking massacre that claimed 1,000 lives.

This narrow canyon has been carved by the river over thousands of years into spectacular and curious forms.

This scalding hot river was thought to be a myth until one geoscientist made it his quest to study the mystical waters.

This Argentinian hedge maze is an intricate tribute to a famous surrealist author.

Mother Nature outdoes herself with this stunningly beautiful set of caves carved into marble.

At the most northwestern point of the contiguous United States lies a trail leading through an ancient forest to stunning cliff-side vistas and massive oceanside caves.

The eerie remnants of an ancient forest were hidden under the sand for centuries.

A French valley with forests so lush it was nicknamed "the Small Amazonia of the Pyrenees."

A grove of "candelabra redwoods" deep in California's Lost Coast.

A long spiraling walkway winds through the woods, and around a copper beech tree at the center.

A pretty park of over 1,600 olive trees that grew from just three saplings brought over from Spain.

The damming of the Colorado River buried an iconic geologic formation before record-breaking drought brought it back.

Ecuador's largest Incan ruins show evidence of sophisticated irrigation and diplomacy among the ancient builders.

The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

Where dogs like the rare "Fire-Tailed Border Cocker" run free on the mountainside.

This Costa Rican topiary park is a surreal garden of unearthly delights.

This neon blue river gets its color from a unique mix of bacteria and volcano minerals.

This modern labyrinth lies in the shadow of a ruined medieval castle.