One-layer pyramid in Indiana.

Entombed in this strange, white stone hill are the deadly remains of radioactive weapons production.

A stunning, abandoned limestone quarry in southern Indiana provided the stone to erect the Empire State Building.

The only freestanding table rock formation east of the Mississippi.

The Magic House provides a beautiful and creative environment for curious youngsters to get their knowledge on.

What was once a presidential estate is now an exotic menagerie and home to the Budweiser Clydesdales.

Symbolic attempt to overcome the issues of life.

This open air cathedral invites all faiths to worship under the only roof big enough to fit them all: the sky.

This titanic oil company sign is a reminder of the Americana boom of the 1970s and also its commoditization.

University City's quirkiest resident lives in a park named after its first.

This is not your typical jungle gym.

A chessmaster's dream destination.

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

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

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

Man-made geyser that rises to the exact height of the Gateway Arch.

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

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

Fresh wooden posts have been added to ancient holes to recreate a primitive henge clock.

Quirky water tower advertises the long-gone Brooks Tomato Products Co.

First known as the "Sample House," this construction mash-up was meant to be a living catalogue of building styles.

A notorious Route 66 eatery once frequented by Al Capone.

This life-size bronze statue remembers the tallest recorded human in his Illinois hometown.

The world's largest collection of the world's largest objects is in one small Illinois town.