Once the "Eighth Wonder of the World," this iron railroad bridge was decimated by a tornado.

This once-grand marvel of engineering is now 41 miles of scenic hiking trail.

Perfectly preserved ancient monastery in an impossibly dramatic location on a rocky island in the Atlantic.

The world's tallest shot tower—maybe.

Relics of Australia's convict past, and a modern scene of unimaginable horror.

The seawater playground of gilded-era San Francisco burned to the ground in 1966.

A daring D-Day assault by U.S. Army Rangers is commemorated atop the high cliffs of this strategic point.

Abandoned Nazi train station turned underground astroparticle laboratory.

Now abandoned, the first public health hospital in the U.S. saw more than one million immigrants from around the world.

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

An abandoned saucer-shaped monument in the Bulgarian mountains.

An abandoned 1920s school with a mysterious history.

The "mysteries" of this quintessential roadside oddity were almost destroyed by neglect but were saved by fans of kitschy wonder.

Once connected to the outside world by a single train track, this ghost town is looked after by the National Park Service.

Hikers can still stroll beneath the long conveyer of this abandoned mining facility hidden in a West Virginia river gorge.

The sinister ruins of one of the worst dam failures of the 20th century lie in this astonishing alpine setting.

A site where “the ravages of the war are more striking…than any other place in contemporary Spain.”

A hidden "place of interment for gentlemen."

This natural French spring has been turned into a magical grotto by Roman and medieval constructions.

Why have you never heard of the second most popular tourist site in New York?

A Victorian park cemetery, standing on the site of what was once the Great North Wood.

A historic arboretum and non-conformist, non-denominational park cemetery.

The sixth of London's "Magnificent Seven" cemeteries, and a source of unlikely inspiration to Beatrix Potter.

A haunting statue called "Eternal Silence" has quite the reputation among visitors with active imaginations.