A century-old network of freight tunnels underneath the city's historic business district.

This unauthorized stone mermaid was secretly carved out of public stone before being permanently preserved.

An antiquated German apothecary on Chicago's North Side.

A science teacher's dream.

A lush green oasis in the middle of Chicago.

A Bibliophile's Dream.

A speakeasy takes on Chicago's drinking culture.

This shop for all your super spy needs hides an educational secret.

This massive stained-glass masterpiece is thought to be the largest Tiffany dome in existence.

This whimsical Oz-themed park had a wonderful impact on the surrounding neighborhood.

A huge musical instrument played by the ocean.

This was once the home of Gahan's Saloon, Denver's most storied speakeasy.

This museum offers an actual time machine back through Colorado's past.

The huge collection of paintings of the American West is one of Denver's best-kept secrets.

A small horde of mythical creatures lurk almost imperceptibly within the museum's wildlife dioramas.

Where scientists keep miles of very valuable ice from Antarctica and Greenland from melting.

A technicolor place of worship for Elevationists.

A beloved, quirky little fountain featuring a large frog spitting water at a naked boy.

Undone by Prohibition, this abandoned brewery-turned-flour mill is now ready for its third act.

This giant green head remembers one of America's jazz giants.

An abandoned concrete jungle surrounded by a lush park.

A piece of John the Baptist in the American heartland.

A cave 150 feet beneath Kansas City is the perfect climate for growing 10,000 delicate orchids.

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