This underground museum highlights the history of Mexico City's subway system.

One of the world's richest men bought this former paper factory and transformed it into a mall.

Many people don't realize there’s a lot going on in—and below—the world’s tallest triumphal arch.

The only castle in North America to ever house European sovereigns.

This punny mirror of another Wisconsin attraction is exactly what it sounds like.

One of the largest aviation events in the world brings half a million aircraft enthusiasts to Wisconsin each year.

As the glaciers retreated out of northern Wisconsin, this unique natural wonder was crafted.

The remains of a enormous earthen figure of unknown origins cuts across a rural Wisconsin road.

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

A theme park attraction designed to turn your children into LARPers.

Over thousands of years, this slot canyon was carved out of the bed of an ancient lake.

A giant, Gilded Age mansion that once belonged to the beer baron of Milwaukee.

Wisconsin's most celebrated export gets the royal treatment on I-94.

This cave holds a surprisingly colorful variety of geological oddities.

These Great Lakes sea caves accessible by boat in the summer turn into temples of ice reachable by foot in the winter.

A bizarre house filled with an astounding array of collections.

The palatial McDonald's that inspired Wesley Willis.

This 4,000-acre restored grassland in northern Illinois is home to a range of native flora and fauna, from clovers to plovers to a herd of bison.

In 2004, a Dave Matthews Band tour bus dumped 800 pounds of waste off a bridge and onto an unsuspecting tour boat below.

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

Burial mounds of prehistoric Native Americans who lived along the DuPage River.

A tribute to one granddaughter's old apartment which now represents the whims of each visitor.

At the largest railway museum in the United States, you can see everything from an early steam engine to a functioning Thomas the Tank Engine.

The sign to a demolished amusement park now stands in front of a local library.