John Hendrix predicted the creation of the "Secret City" built as part of the Manhattan Project.

Ethereal alien hums and haunting whale songs emitting from...a giant sheet of vibrating metal?

This mansion turned restaurant was once a pitstop for Al Capone during his travels.

One of the Cemestos prefab homes built to secretly house thousands of Manhattan Project workers.

This tiny 19th-century tunnel was built so a man could move his cows from one field to another.

Victorian-era Egyptomania left its mark on this Nashville landmark.

Dinosaurs invade a suburban Nashville neighborhood.

The world's largest collection of porcelain "veilleuses-theiere," or night light teapots, includes four that belonged to Napoleon.

This large cave is a summer home to thousands of bats and has a rich history dating back to prehistoric times.

Once decrepit and slated for demolition, now one of the longest pedestrian bridges in the world.

Knoxville’s architectural icon was the symbol of the 1982 World’s Fair, even catching the googly eye of Bart Simpson.

The juke joint where legendary soul artists ate, drank, and made merry.

This historic train station has been converted to a locomotive themed hotel.

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

The first full-scale tunnel built in America is short but scenic.

This Memphis recording studio launched the careers of Jerry Lee Lewis, Johnny Cash, and Elvis Presley.

Live long and prosper in Tennessee.

Every day a troupe of pampered water fowl walk the red carpet to their favorite fountain.

This head-spinningly bizarre Depression-era art cave is wall-to-wall quartz and Jesus.

The hotel where Martin Luther King Jr. was shot is now a museum dedicated to his work.

The mysterious wonder of an underground waterfall is illuminated by multicolored lights.

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

Enormous lake at the bottom of a unique cave system.

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