The "World's Largest Underground Business Complex," a 55,000,000-square-foot city underneath Missouri.

The world's largest man-made underground caverns offer unparalleled underwater wonders.

European castle ruins in an American state park are actually the product of death and grief.

Less a museum than a bizarre fantasy world created by artists and engineers.

This abandoned prison castle has become an imposing gallery of graffiti art.

Once an ambitious nature spa, these forest ruins now provide a serene monument to failure.

The history of the treatment of mental illness, illustrated in all its gory detail, and housed in an asylum.

If there's another drive-through golf-cart bar in a bat-filled cave on top of a mountain, we don't know about it.

This mosaic-covered bar is brimming with curated curios.

A creepy sculpture of a decapitated head invites viewers to see St. Louis through its empty eyes.

Curious cave that stays a cool 56 degrees all year long.

Community bookshelf of 25-foot-tall book spines.

This is not your typical jungle gym.

A historic house in St. Louis was plagued by a series of suicides committed by family members involved in a successful brewery.

Erosion and time have created a naturally-formed water park.

400 million-year old limestone caverns nestled in the Ozarks served as shelter and a hideout for cultures throughout North American history.

A remarkably opulent mansion with a tragic history.

A 35-foot-tall fork stuck in the ground outside an office building in Missouri.

A kitschy, creepy St. Louis mainstay.

An unexpected but incredible collection of wildlife dioramas spanning rainforests, swamps, forests, and plains.

A mysterious light of unknown origin on the backroads of Missouri.

The red brick house where the father of rock 'n' roll wrote some of his classic hits.

A big museum full of little worlds.

The oldest bar in Missouri is hidden within a limestone brewery cellar more than 50 feet underground.