One of the largest-ever mental hospitals now sits abandoned, surrounded by 25,000 unmarked graves.

These eerie outliers of the lightning bug family glow a mysterious blue color.

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

This road in the Great Smoky Mountains was supposed to assuage a displaced community, but ended up a $52 million dead end.

This natural wonder drops 16 stories straight down through rare flora and streaming waterfalls.

Crumbling ruins mark the site of a couple's grisly murder in the woods.

A curious whirlpool formation supposedly capable of entangling or engulfing branches, tree trunks, or whole rafts full of hapless tourists.

A secret, rocky playground hidden amongst the plain white beaches of the Florida coast.

Two men built this castle on the Florida coast as an artistic “landscape sculpture.”

The only Florida state park with publicly accessible caves.

The highest point in Tennessee, Clingmans Dome bears witness to the ravages of one type of insect.

The perfectly named cave drop is the deepest in the continental United States, almost matching the height of Seattle’s Space Needle.

Where school buses go to die and be reborn as whimsical works of art.

An impressive collection is dedicated to the legendary beast.

They call this long foot bridge a swinging bridge, but really it's the bouncing you have to watch out for.

The statues commemorate the legendary mass killing of escaped circus monkeys.

Who needs fancy modern water slides when this giant North Carolina rock works just as well?

Rippling sand dunes frozen in the Arizona rock.

Dramatic river bend surrounds a natural red-rocked pedestal.

Most-visited and most-photographed slot canyon in the American Southwest.

Eons ago, a rushing lava river formed this pristine passage through solid rock.

Finale of "William Tell Overture" can be heard as drivers pass over grooves in the road.

Trails through lava-carved tube-caves display sparkling bacteria and a rich history.

A trash dump made beautiful by nature's power.