Read between the lines of the subway map to find the hidden abandoned Civil War fort.

There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.

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

Visible below the waves are memorials to the city's Gold Rush dead.

New Orleans' famous cemetery, located on the site of a former race track.

Home to the infamous "Typhoid Mary" and the worst loss of life in New York's history prior to September 11, 2001.

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

A particularly creepy abandoned hospital that sparks interest for lovers of the supernatural.

This charmingly homemade amusement park has been growing for 40 years.

Enormous piles of historically significant stones, dumped by Congress in a forest, and abandoned for 60 years.

An enormous park-like oasis, full of famous Chicagoans' graves.

The second oldest continuously operating bar in Louisiana.

An abandoned stretch of highway, deteriorating next to the operational one.

The largest earthwork effigy in the world.

The remains of an idyllic small town built for the film 'Big Fish' still stand around a rundown main street.

This cemetery has graves dating back to the 17th century, including the city's oldest carved tombstone and an ominous cryptogram.

This historic "City of the Dead" lies prominently in the center of New Orleans' famous Garden District.

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

These delicate buggers are some of the rarest fossils that have bubbled up from the Tar Pits.

Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.

This abandoned asylum was once a state of the art facility before devolving into one of the most deadly mental institutions in American history.

An underwater city for the dead.

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

A heavenly experience, right here on Terra Firma.