A hidden network of subterranean passageways lies tangled beneath Indianapolis' bustling City Market.

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

In the Shawnee National Forest, amazing rock formations peer through the treeline.

An exhibit of items from the mental institution where Mary Todd Lincoln lived after her son conspired to have her committed.

The only place in America where anyone who wants can shovel coal aboard an antique train.

A historic and oft-filmed prison stands in a Chicago suburb.

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

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

This cheerfully-named branch of the Chicago River is the fetid result of years of blood, entrails, and meatpacking waste.

This abandoned 19th century orphanage started as a boarding school for children of Civil War veterans.

A river with some unusual, and occasionally dangerous, habits.

A notorious Route 66 eatery once frequented by Al Capone.

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

Eclectic collection of rare and beautiful stones in a historic home.

The legacy of an unsolved, gruesome murder rests beneath the spans of this historic bridge.

What was once the second largest steel mill in the US is now a sprawling complex of modern ruins.

This grave in a ghost town cemetery marks the death of a witch on a day that never happened.

This alley in downtown Chicago held the bodies of over 600 people after the fateful Iroquois Theatre fire.

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

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

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

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

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

The only retired U.S. nuclear missile silo that is open to the public.