A mythical bird etched into the face of a rock doubles as the mascot for a nearby school.

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

The longest navigable underground river in the United States is home to countless blind and albino animals.

A turn-of-the-century architectural marvel built on healing mineral springs and salt licks.

The show pony of cave systems, Fantastic Caverns manages to live up to its name.

Moving, mind-blowing metal sculpture work of an outsider artist.

River pirates, murderous bandits, and serial killers used this Illinois cave as their debauched hideout.

Where the author wrote her beloved "Little House" books.

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

The park that the Chicago Stockyards built.

You were once able to challenge a chicken to tic-tac-toe at this park, which is now converted into the Aikman Wildlife Adventure.

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

Center filled with hands-on displays served as a tribute to several astronauts with connections to the state.

The largest earthwork effigy in the world.

This sprawling mini-golf empire is an impressive testament to a disappearing attraction.

The remains of a Rockefeller's lush Italianate estate hidden in the underbrush on the coast of Lake Michigan.

This elaborate Hindu temple is located in a Chicago suburb, but looks like it was transported directly from India.

A Bibliophile's Dream.

Four glass boxes hover over 1,000 feet in the air to give visitors an unparalleled view of Chicago.

A lush green oasis in the middle of Chicago.

At Chicago's revered Field Museum, visitors are invited to learn about and literally explore DNA.

This historic-shipwreck-cum-diving-spot can still be seen poking its boiler out of the Lake Michigan waters that claimed it.

This Mediterranean castle was built for a millionaire and his giant dog.

Tour the luxe "glass cage" that inspired and unnerved the architecture world upon its debut.