The art studio of an early 20th-century painter, hidden amid the Great Smoky Mountains.

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

This giant ice cream cone is the last remaining icon of a Salt Lake City staple.

The world's largest egg has been cracked a number of times over the years but has been repeatedly replaced.

Children's literature inside, forest all around.

The rustic think-space of famed naturalist John Burroughs stands exactly as he left it.

The remains of a century-old mansion that met a fiery demise years after it was deserted.

America's first public mental health facility.

A building shaped like the Army Corps of Engineers logo, because why not?

The most accurate timepiece in the world.

The now-overgrown beach resort was once frequented by Yugoslav military elite.

A hoard of sky catalogs, astrophysical journals, even the works of Galileo and Copernicus.

In the basement of the U.S. Capitol Building is a hidden storage room full of ornate floor tiles leftover from the 1850s.

This improbable contraption was passed down through five generations of industrious Tennesseans.

One of the world's richest men bought this former paper factory and transformed it into a mall.

After starting as a whimsical tourist attraction that eventually found its way to ruin, these renovated canals offer a lush and exotic locale on the Pacific Coast.

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

Daredevil repair workers can worm their way out the access hatch, loop ropes over the apex and rappel down the monument.

This bridge is haunted by the ghost of a distraught mother.

The enormous 250-room Vanderbilt mansion conceals hidden doors and secret passageways.

This Transylvania County city is home to a rare white squirrel population that is descended from an escaped carnival animal.

According to local lore, this narrow passageway through two large rocks was accidentally created by the devil himself.

The opulent car collection of an eccentric Sheikh housed in his own private pyramid.

Step back in time at this 1950s display home, built to showcase once cutting-edge electric amenities.