A slab of sandstone covered with mysterious 1,000-year-old rock carvings from a vanished North American culture.

Moonbows over Kentucky.

The largest earthwork effigy in the world.

Once the extravagant escape of the Ford family, this enigmatic ruin now stands as a haunting reminder of its former glory.

This unusual three-way wooden foot bridge spans two rivers at once.

This experiment in the lifespan of seeds will take a century before it is complete.

An eerily abandoned stone tower is all that remains of a demolished dam on Cape Fear River.

A sculptor's dream castle turned fantastical ruin.

Famous for its bio-luminescent inhabitants, known as "Dismalites" .

Once the world's largest reinforced concrete structure, this abandoned bridge now beckons urban explorers.

Buildings that dynamite couldn't bring down were abandoned because of bathroom issues.

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

An abandoned coal mine reached by a steep hike.

One day a year it is legal to jump off of this astoundingly tall bridge that spans an Appalachian gorge.

One of the few surviving examples of the first lock and dam system built on the Ohio River.

These World War I shooting range tunnels are now haunted halls of underground graffiti accessed through the roots of a tree.

This huge, disused viaduct is now a crumbling concrete underworld of covered in years of graffiti.

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

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

The headquarters of a pioneering cast iron and cast aluminum cookware company is in ruins, but still standing.

The overgrown remains of an old rail bridge rise above the valley like ancient Greek ruins.

The ruins of the suspension bridge hang over Kingsbury Run as a ghost of racial prejudice.

This railroad overpass is said to be home to a murderous goat-man whose very legend has led to very real deaths.

A ship that lived many lives under many names is now known merely as the "Ghost Ship."