A little-known subterranean street runs under some of the best-known buildings in Chicago's River North.

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

A century-old hotspot for jazz, frequented by everyone from Charlie Chaplin to Al Capone.

This historic hotel invented the chocolate brownie.

A European-style bath house in Chicago.

Years of archaeology, just chillin' by the water cooler.

Former hotel turned into haunted playground.

The world's only known button museum.

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

The site of the first couple's first kiss is commemorated by the most adorable presidential monument ever.

A once-booming Mississippi River town with a history of racial violence is now eerie and mostly abandoned.

What was once one of the country's largest confectionary plants is now an abandoned ruin, but is still pretty sweet.

What's left of the ruins of the 1893 Columbian Exhibition, or World's Fair, also known as the White City.

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

A hollow cement depiction of time's inexorable effect on the human body.

Nonprofit art center that promotes outsider, intuitive, and self-taught art.

A gothic church spire sits atop this skyscraper, the tallest church in the world.

A haunting statue called "Eternal Silence" has quite the reputation among visitors with active imaginations.

A lush green oasis in the middle of Chicago.

Shop of curiosities with a dinosaur museum tucked in its basement.

A science teacher's dream.

A Bibliophile's Dream.

A giant bronze coil of feces is both a tribute to doggie defecation and a reminder to pick it up.

A monument to the art of slicing people open.