Smoked mummies housed in mountainside caves.

Site of the largest impact event to occur over land in Earth's recorded history.

A swing to dangle you off the very edge.

A serpentine highway twists and turns over the treacherous Norwegian Sea.

This natural Icelandic fissure allows divers to swim right between two volatile tectonic plates.

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

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

A massive underwater sinkhole made famous by Jacques Cousteau.

An enormous, 30-story-deep hole in the middle of Guatemala City.

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

Natural time capsule containing an alien ecosystem.

Not one, not two, but three natural bridges remain in this captivating spot post-sinkhole.

A volcanic old faithful, Stromboli has been erupting continuously for the last 2000 years.

One of the highest emergency huts in the world has been waiting almost a century to give imperiled climbers a place to lie down.

This dormant volcanic crater has been converted from a roiling pit of magma to a pleasant hiking spot.

A Netherlands hotel where you can sleep inside a wine barrel.

This series of rope-style bridges brings visitors into a jungle layer that is usually reserved for birds and monkeys.

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

One of the most remarkable caves in all of Iceland was created by a once raging river of lava.

An extraordinary "City of Caves" carved from solid stone.

The world's oldest surviving anatomical theater, where "the dead are pleased to help the living."

Berlin's oldest surviving academic architecture hosted decades of animal dissections.

A phenomenal assembly of pueblos in New Mexico is the most complete example of ancient ruins north of the border.

This Navarrese cave's history of witchcraft and pagan ritual is not just embraced, but recreated each year.