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

World's second largest particle accelerator, where nature reveals its secrets.

A sprawling outdoor museum filled with larger-than-life works of art.

This historic Illinois "Muffler Man" has been converted from axe-touting lumberjack to rocket-wielding space ace.

A historic and oft-filmed prison stands in a Chicago suburb.

What was once the second largest steel mill in the US is now a sprawling complex of modern ruins.

The final resting place of the world's first nuclear reactor.

This supper-club-turned-concert-venue still serves drinks at its original rotating bar.

This crumbling stump is all that remains of what was once thought to be the oldest living organism.

This lush 12-acre site was once named the finest Japanese garden in North America.

This small turbine mill along Rocky Creek was built in 1928

A 40-foot waterfall flows into this unique natural swimming hole.

The deepest spring in Missouri.

The lowest point in the state of Illinois, at the confluence of the Mississippi and Ohio rivers.

A once-booming Mississippi River town with a history of racial violence is now eerie and mostly abandoned.

Often referred to as the largest spring in America.

The only mill in the state that features a covered bridge.

In the St. Francois Mountains in the Ozarks at 1,772 feet above sea level, Taum Sauk Mountain is the highest (and possibly oldest) peak in Missouri.

Thousands of unique minerals, including some of the most impressive fluorite crystals in the world.

An enormous natural sandstone bridge in Kentucky.

You have to love a museum with a truly dedicated focus. A focus on Superman, for example.

A collection of outdoor art by renowned muralist Robert Dafford depicts the history of a flooded city.

A whimsical folk art garden full of punny pieces and a diorama containing 3,500 toys.

In Rickwood Caverns, visitors can travel hundreds of feet underground and see beautiful formations unique to the region.