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

A rapidly disappearing authentic bit of the old south.

Live long and prosper in Tennessee.

More than five miles of underground passageways.

This funicular railway rumbles along for a mile up the nearly vertical face of Chattanooga’s Lookout Mountain.

The world's largest set of the ten commandments lay nestled in the heart of the Great Smoky Mountains.

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

An impressive collection is dedicated to the legendary beast.

The mysterious 855-foot zigzagging stone wall has been baffling people for centuries.

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

An abandoned railroad tunnel forgotten by time awaits inquisitive hikers.

This ever-changing arrangement of naked dolls even caught the attention of "The Walking Dead" crew.

The ruins of a cotton mill that was burned in the Civil War are still hidden in a Georgia forest.

One man's vast collection of artifacts and ephemera from matchbooks and postcards to vintage neon signs and cars.

A walk-in working camera obscura produces 360-degree live images of the San Francisco coast.

The only theatre in the world constructed specifically for sound movement.

A psychedelic labyrinth on the San Francisco bay.

A 140-year-old castle with underground caves hidden in San Francisco.

One of the last full-orchestra recording studios in New York City and an acoustical marvel.

Red frames showcase remnants of one of New York's original subway stations.

An annual extravaganza of Broadway theater memorabilia.

The former home of the reclusive "Weird Wendels" who dominated New York real estate a century before Donald Trump.

The smallest island in Manhattan is a manmade landfill dominated by a Buddhist peace arch.

This study room in the New York Public Library saw the creation of one of contemporary America's greatest traitors.