Once one of the largest producers of pig iron in the world.

This 1,500-acre development hopes to be the Central Park of the South.

A collection of huge Pre-Colombian structures in Alabama.

One person's lost luggage is another person's treasure.

Once a bustling cotton factory, this early 20th-century building is now home to a thriving artspace.

You'll need cowboy boots to trek to this old-fashioned saloon nestled in a giant natural cave.

The world-record holder for the longest bridge stretching continuously over water.

One of the only Florida forts to remain in the hands of the Union all through the Civil War still stands as a historic stronghold.

A building so large that it has its own weather.

Ruins of a Carnegie family mansion on Cumberland Island.

These mysterious ruins are hidden amid this sleepy coastal city.

A snapshot of the city's fascinating voodoo culture.

The second oldest continuously operating bar in Louisiana.

Storyville was New Orleans' historic red light district and hotbed of jazz music, sometimes referred to simply as "The District."

One of the longest water bridges in the world was built over a supposedly haunted swamp in Louisiana.

Once one of the world's great cities, Cahokia was a place of religious worship, trade and mass human sacrifice before being mysteriously abandoned.

A hidden network of subterranean passageways lies tangled beneath Indianapolis' bustling City Market.

The largest historic preservation organization in the United States.

Once adorning a New York skyscraper, these reclaimed ruins now haunt an Indiana park.

This Florida sinkhole hides a rainforest-like micro-environment in its depths.

A medical facility that has been kept frozen in time.

A small metropolis of Pueblo cave dwellings have been carved right into the hillside of this national monument.

A Lycian city of the dead carved into the hillside of Southern Turkey, complete with startlingly human touches.

A pocket of jungle amidst urban expansion in Panama.