A wonderland of caves in eastern Iowa.

This cave holds a surprisingly colorful variety of geological oddities.

Inspired by a piece of concrete, these three pyramid-shaped buildings have been beloved Indianapolis landmarks for over 50 years.

A journey begins with a single step, and for many, the road-trip of a lifetime started at this Chicago intersection.

These chunky stone towers out in Lake Michigan are the key to Chicago’s drinking water.

This memorial plaque remembers a strangely shallow maritime disaster known as "Chicago's Titanic."

Its eclectic exhibits range from the world’s first motorcycle to Luke Skywalker’s Land Speeder.

A small abandoned and abused cemetery that has become a magnet for ghost hunters.

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

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

An enormous park-like oasis, full of famous Chicagoans’ graves.

A lush green oasis in the middle of Chicago.

One of the finest examples of a black soil prairie that was barely saved by the Great Depression.

World's second largest particle accelerator, where nature reveals its secrets.

The last masonry skyscraper ever built reveals a transitional moment in architectural history.

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

Illegal drag racing two stories beneath Chicago’s streets.

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

Meant for a railway that was never built because of the Great Chicago Fire, these piers still stand nearly 150 years after they were installed.

A remnant of the last Ice Age, this lake is surrounded by fascinating rock formations.

This former nursery supplied plants for the creation of Chicago's largest park.

Today this bizarre rooftop phone booth seems like a piece of kitsch but it was once used to spot disastrous storms.

This national park dedicated to the tallgrass prairie ecosystem still displays its military past.

A spectacular remnant of an Adler and Sullivan masterpiece that was destroyed in 1972.