These azure waters were thought to lead to the Mayan Underworld.

A stunning, two-tiered waterfall made famous by poets, artists and the legend of a ghost dog.

Natural time capsule containing an alien ecosystem.

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

Carved by a waterfall in a hard-to-reach rock formation, this heart-shaped rock has inspired romantics for decades.

A winding path built in secret on the edge of the continent.

Centuries-old bridges grown from tangled roots.

Every autumn, this hillside is ablaze with red summer cypress.

This fantastical waterfall is hidden in a cave located in a cracked cliff.

A beautiful geyser under environmental threat.

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

Museum preserving torture methods from the past.

An ethereal glowing blue ocean cave in Croatia.

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

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

A gargantuan crystal kingdom.

These old stone ruins in the Oregon wilderness were once bathrooms and are steeped in legends of murder.

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

An alchemist's "magic door" stands in the middle of a Roman park.

A natural gas leak provides a flickering flame beneath a waterfall.

Stroll through a wonderland of stupendous moss-covered trees.

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

In this historic region, homes and churches are carved into ancient volcanic rock formations.

One of the world's oldest and most massive living organisms is a grove of quaking aspens.