An abandoned lot littered with concrete debris was once the home of the world's first female railroad president.

The deepest underground city in Turkey was designed to protect 20,000 people behind massive stone doors.

The Empire Mine is "one of the oldest, largest, deepest, longest and richest gold mines in California."

To literally keep their waste out of their own backyards, the citizens of this English city built an impressive sewer system that is still in use today.

The longest navigable underground river in the United States is home to countless blind and albino animals.

The second largest in the world, this massive underground void has its own subway.

This natural history collection contains the bones of a circus elephant that seem to be chasing a whale skeleton.

A wunderkammer hidden on the top floor of the Hartford statehouse.

This abandoned subway station beneath the Waldorf-Astoria hotel is allegedly used to secretly transport presidents.

This series of underground chambers contains Europe's largest subterranean lake that is slowly drained each day.

A former copper mine which became a truly unsuccessful prison.

Underneath the city that invented pilsners are a series of historic tunnels that have been storing beer for centuries.

The labyrinthine storm tunnels beneath the city of Melbourne are ruled by a band of urban explorers.

What was once thought to be a wellspring of unicorn bones is actually just a prehistoric burial site.

Staves, storm-calling, and of course, necropants.

This real life asylum of horrors is now an abandoned ruin that hides the unbreakable code to one patient's insanity.

This lush forest valley was once mined for lumber to the extent that it was once nicknamed "The Pennsylvania Desert."

This former Welsh metal factory is now a lovely abandoned relic but was once one of the industry's world leaders.

Another of California's unused Cold War missile defense complexes has become a graffiti gallery.

A once crucial portion of the Long Island railroad still lays abandoned, waiting to be turned into an urban park.

This tiny New Jersey village has lived many lives but seems determined to remain a ghost town.

This stunning gothic ruin was a casualty of the Indiana steel industry crash.

The final remnant of the Arkansas zinc industry is this historically protected ghost town.

This small group of sand dunes manages to pack in a strange rainbow of colors.