An Italian hillside ghost town.

The origin of this mechanical boy was a mystery until he revealed his maker by writing it in perfect cursive.

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

This once-palatial plantation may have been the site where a draft of the Declaration of Independence was written.

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

San Francisco Bay's ghost town.

An abandoned quicksilver mining town surrounded by the Big Bend parks.

Abandoned power station once home to a squatter community, now being developed into an arts center.

One of the ghostly stops along Route 66.

A well-preserved Ancestral Puebloan ruin tucked beneath a desert cliff.

A once grand hotel is being retaken by the wilderness it once capitalized on.

The hallucinogenic center of the ancient world.

A picture-perfect town, perfect for blowing up.

A phenomenal assembly of pueblos in New Mexico is the most complete example of ancient ruins north of the border.

Once the most densely populated place in the world, this island is now a ghost town.

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

An ancient capital city that dates back 3,000 years old and harbors many surprises.

The world's longest known cave system.

One of the world's oldest and most massive living organisms is a grove of quaking aspens.

The ghostly remains of an accidental sea.

The secret city built by the Manhattan Project.

Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.

A beautiful 62-acre Catholic shrine and botanical garden.

Where America's first doomsday cult awaited the end of the world.