This army of concretions is an unexplained geological phenomenon unlike anything else in the world.

A cave's rare beauty held a cavernous secret hidden underground.

The world's longest known cave system.

A charming beach town in Turkey captures all the colors of the rainbow.

This Turkish cave boasts some rather bizarre associations with the King of Mount Olympus.

A galaxy of glowworms—larvae of a gnat—hides deep in the belly of these caves.

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

Bioluminescence in the reefs of the Maldives causes the sea to glow like a starry night sky.

A lovers' beach, tucked below the surface of the island, provides a safe haven for romance.

A spectacular hidden beach in Ireland has the dark, disturbing nickname of "Murder Hole Beach."

Constant erosion has created a surreal landscape of bleached and preserved fallen trees.

A hidden beach at the end of a tunnel of mangrove trees.

In Portugal, a secluded stretch of untouched natural beauty hides at the bottom of a steep hill.

A unique seaside cave where Aleister Crowley faked his own death.

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

Curious cave that stays a cool 56 degrees all year long.

A preserved stretch of ancient fossilized trees with an impressive gem collection to boot.

A rugged lava field dotted with molds of the ancient pines that were growing when the volcano erupted.

Impressive sink holes fill this untouched old-growth forest in the Bahamas.

One of the most remote lodges in the Amazon offers rare wildlife encounters and undisturbed views of the Peruvian rainforest.

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

Woven tree art gives this towering Australian woodland a touch of mystical whimsy.

Crooked windswept pines give this old forest an enchanted and magical look.

A trash dump made beautiful by nature's power.