The world's highest and most dangerous infinity pool lies at the precipice of Victoria Falls.

The world's second-largest excavated hole.

148 feet long and in the middle of a verdant forest.

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

The ghost town left by the worst nuclear disaster of all time is being taken over by nature and urban explorers.

A theme park that suffered massive flooding during Katrina was abandoned, and now proves irresistible to trespassing explorers.

An underwater city for the dead.

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

Sparkling, calcite-covered skeletons of children who may have been sacrificed to appease an angry god.

A massive underwater sinkhole made famous by Jacques Cousteau.

The world's longest known cave system.

A miniature train-ride through Slovenia's largest cave system.

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

Storage units with a wartime past.

This one-time health resort was used by aristocrats around the world.

A natural arch offers panoramic views of Yangshuo's karst hills.

An ancient iron pillar in Delhi that seems to be rustproof.

This medieval castle overlooking the Elzbach river looks just like it did hundreds of years ago.

A Mayan village preserved for centuries in volcanic ash.

The water in this preserved area spawns vegetation that gives it a deep green color.

270 million year-old forest of stone.

Apartment complexes built into huge repurposed natural gas tanks.

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