Once the "Eighth Wonder of the World," this iron railroad bridge was decimated by a tornado.

This abandoned Poconos resort is haunted by a history of kitschy romance and a violent fugitive.

These beautiful ruins deep in the Pennsylvania woods are thought to have been a ski lodge or a speakeasy, but no one really knows.

Sail through this subterranean show cave that is home to a legend that would go on to name nearly everything around it.

Deep under Manhattan is the largest construction project in city history. So far, the project has taken the lives of 23 workers, or "a man a mile."

Visit the site of a subway powered by nothing more than air--and lots of it.

Hiding the longest subterranean river known in the world.

Now overgrown, these anti-tank barriers from World War II are sometimes called "dragon's teeth."

Two standing giants remain as a tribute to Luxembourg's metallurgical past.

This noble mash-up in eastern Luxembourg is part Medieval, part Renaissance, all castle.

This historic hiding place, often used by people escaping slavery, is a testament to a heroic struggle for freedom.

The hike to this stunning waterfall on a black sand beach is not for the faint of heart.

This mountaintop lake bubbles and steams in a perpetual boil, thanks to its direct link to the Earth's interior.

A flower grows on this giant stone that is said be able to control minds.

An ancient city hidden in the heart of the Sierra Nevada mountains.

The caldera of this mini-volcano has been turned into a naturally heated mud bath.

Enchanting cave with a river crashing through the roof.

An explosion of natural color known as "the river that ran away from paradise."

A 10 million-ton rock once worshiped by the Tahamies Indians, accessed by an astounding staircase.

Ripped apart by a bomb in 1993, the shell of Pablo Escobar's infamous vacation house still stands.

The Andean town where every single building is decorated with a brightly colored frieze.

Former drug lord’s manor, now a theme park. Watch out for the hippos.

Cathedral carved out of salt, located a mile below the earth's surface.

This colonial town in Colombia sits around the largest stone paved square in South America.