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

Collapsing castle on the Hudson river was once the storage site of military surplus business.

The fairy tale castle of the "fairy-tale king."

The inspiration for H.P. Lovecraft's horror stories and Batman's Arkham Asylum is now a condominium complex.

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

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

A castle built by an eccentric medieval enthusiast in rural Ohio.

The largest burial mound in the United States holds the remains of prehistoric West Virginians.

Georges Seurat’s pointillist masterpiece has been recreated in Ohio in topiary form.

The only remnant of a small mining town is an abandoned railroad tunnel that is steeped in ghostly lore.

An abandoned asylum incorporated into a college campus.

A favorite of Amelia Earhart, ranking among those rare bridges that can be crossed without changing sides of the river.

This former tuberculosis research hospital endeavored to cure the dreaded disease with fresh air and positive attitudes.

A life-sized memorial to Harry L. Collins, the official corporate magician of Frito-Lay.

This abandoned cemetery has a dark past of bodies buried over bodies.