The intricate stonework of Machu Picchu serves as a testament to Incan engineers.

One of the few remaining casualties of the London Blitz, this destroyed church has become an enchanting public garden.

A crumbling hospital from the 1850s on Roosevelt Island.

World's first "penitentiary," meant to be humane, drove men insane.

This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

During prohibition, corrupt city officials ran drinking dens under the streets of Downtown Los Angeles.

London's creepiest cemetery was once the site of dueling magicians and mobs of stake-carrying vampire hunters.

A beautiful and abandoned New York subway station from 1904, complete with chandelier.

The mysterious wonder of an underground waterfall is illuminated by multicolored lights.

More than five miles of underground passageways.

This abandoned bridge to nowhere stands secluded in the woods of a Cleveland suburb.

Superfans of The Shawshank Redemption can take a driving tour of most of the films real locations.

What is it about mushrooms that makes people wish they lived inside of them?

An unoccupied lighthouse encased in layers of ice from the waters of Lake Erie.

These sub-farmland caves are home to a majestic stalactite known as the "Crystal King."

An abandoned relic of the city's failed experiment with below ground transit.

A series of caves under Castle Hill that once held the prisoner Vlad Tepes, better known as Count Dracula.

It might not be the prettiest pyramid in Egypt, but it may be the muddiest.

This museum in a shuttered train station remembers the island's forgotten rail system.