A 40-foot waterfall flows into this unique natural swimming hole.

An average of 33 million gallons of water pour out of the collapsed cave at the heart of this spherical spring.

Often referred to as the largest spring in America.

The deepest spring in Missouri.

This art deco masterpiece was once a miracle spring mecca but is now simply a government office building.

One man's unrequited love stands in a glass box forever.

The crumbling remains of the first Black-owned and operated hospital in Kansas City.

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

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

A piece of John the Baptist in the American heartland.

This historic motel standing at the "crossroads of America" offers a radio in every room and was saved by local protesters.

This historic cliffside mansion uses a natural cave for air conditioning.

An abandoned concrete jungle surrounded by a lush park.

A subterranean haunt where wine and homemade biscottis are always on the menu.

The maximum security facility was once thought to have "the bloodiest 47 acres in America."

A geological oddity formed by two rivers carving out a mass of limestone on both sides.

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

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

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

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

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

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

When Joseph Marconnott died, he had a unique final wish: to be mummified and put on display.

This mausoleum is the final resting place of one of St. Louis's richest and most tragic families.