This replica of the Greek structure is in the heart of Nashville.

More than five miles of underground passageways.

Visit this playground of waterfalls, caves and sinkholes.

Wild lights and sound effects turn a walk through some caves into an eye-popping 1960s tourist attraction.

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

A cemetery for only coon hounds in northwest Alabama.

A propulsion engine testbed that paved the way for the Space Shuttle launch sits without recognition at this rocket center.

It may look like no more than a full-scale model, but every part of this full Space Shuttle stack had a working role in aviation history.

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

The highest point in Alabama was almost completely deforested, but is now home to protected towers and trees.

You'll need cowboy boots to trek to this old-fashioned saloon nestled in a giant natural cave.

148 feet long and in the middle of a verdant forest.

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

Moonbows over Kentucky.

This labyrinth was designed to help visitors focus and meditate.

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

Constant erosion has created a surreal landscape of bleached and preserved fallen trees.

Ruins of a Carnegie family mansion on Cumberland Island.

Bad farming practices caused this unnatural natural wonder.

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

A bizarre roadside attraction and the first instance of miniature golf in the world.

A mysterious monument meant to be a guide into "an Age of Reason" was destroyed after an apparent bombing.

These ancient ritual mounds are our best window into the culture of the ancient Mississippians.

Suspended above the ground in a thicket of towering Georgia trees is a modern architectural wonder.