A rusted blade sticks out from the trunk of this tree, left as a memorial to a young man who left to fight in the Civil War but never returned home.

Explore the dark underground corridors of this graffiti-covered former military fortification.

Kentucky, Tennessee, and Virginia meet at this point in the Cumberland Gap.

For two weeks every June, fireflies in the Smoky Mountains perform an astonishing light show.

The entrance to this sinisterly named tunnel hides behind a Tim Hortons.

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

Take a drunken tour inside the world's largest known geode.

Giant busts of 42 U.S. presidents are sitting in a field in Virginia.

The macabre graffiti spectacle in a quarry in a Massachusetts forest reservation.

This railroad tunnel was once the longest in Massachusetts.

From economic backbone of a community to deadly diving hole, these former stone quarries are now a park for rock climbers and graffiti artists.

Trash escaped from a landfill to fill beaches with all kinds of treasure.

The ruins of a Massachusetts prison farm can still be found crumbling the woods of a state park.

Friction between grains of sand cause a curious "singing" sound.

A miniature village lies nearly forgotten in the forest by the side of a major highway.

A religious-themed park filled with folk art to bring biblical stories to life that fell into disrepair and now being restored.

An eerie, abandoned military base engulfed by nature and graffiti is now home to a local park.

Despite violent work crews and massive delays this abandoned canal tunnel was built to last into the modern day.

A blank headstone topped with a pile of pennies marks the final resting place of the infamous assassin.

A hidden alley in urban Baltimore is a haven for graffiti artists.

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

The haunting "Hell House Altar" is one of the few remnants of an abandoned college that has been a magnet for local legends.

Hidden deep within New Jersey Pine Barrens is a massive graffiti wonderland.

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