One of the most powerful computers in the world can be visited by anyone who wants to experience more computing than they can handle.

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

An amazing collection of scale model ships.

Rifle through images of skyscrapers, Worlds Fairs, and more in the largest public postcard repository in America.

First known as the "Sample House," this construction mash-up was meant to be a living catalogue of building styles.

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

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

A six-story-tall golden pyramid, surrounded by a moat.

An avant garde art museum at the University of Chicago.

These abandoned grain silos and tunnels are an urban exploration dream.

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 European-style bath house in Chicago.

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

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

A science teacher's dream.

A lush green oasis in the middle of Chicago.

The site of a 19th century "dream city" that almost rivaled Chicago before being swallowed by the Indiana sand dunes.

A stunning, abandoned limestone quarry in southern Indiana provided the stone to erect the Empire State Building.

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

This unique wooden mosque resembling a Chinese pagoda was said to be built without the use of nails.

A surprising museum of 20th-century technology.

This freshwater spring fills with 10,000 gallons of water per minute.