The curious underground history of keeping Paris clean.

Once one of the world's great cities, Cahokia was a place of religious worship, trade and mass human sacrifice before being mysteriously abandoned.

These experimental weapons brought World War II to Nebraska as well as 26 other U.S. states.

The only Bahá'í house of worship in North America and one of only a handful worldwide.

A college in rural Kansas founded to prepare the country for an impending World War III.

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.

Giant granite rocks standing end-to-end like a train of circus elephants.

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

An abandoned meat mecca now serves as an excellent locale for urban exploration.

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

A museum dedicated to man's boldest venture.

A floating museum that was sunk by a flood and left to rot in the tides.

A kitschy, creepy St. Louis mainstay.

The Old Courthouse takes visitors on a captivating trip through St. Louis' timeline.

An abandoned factory along the Mississippi coated by a giant mural.

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

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

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

Speak to a companion on the other side of the room loud and clear through this architectural anomaly.

An urban forest overtakes what was the greatest failure of utopic urban housing.

This spot in St. Louis, marked with a simple sign, has seen more pro baseball than just about anywhere else in the world.

A late sculptor's last project was to turn this abandoned cement factory into a castle-themed amusement park.

A big museum full of little worlds.

The first rural cemetery west of the Mississippi is home to the elaborate tombs of St. Louis' local beer barons.