The world's second largest single-dish radio telescope, once used to contact E.T.

Rumored to be the famed pirate's lookout tower, this historic stone structure is now just watching for tourists.

A sharply wedged sundial marks the point at which each day in the United States begins.

The geoglyph once sported a glass bottle eye.

The palatial McDonald's that inspired Wesley Willis.

This unassuming city park is home to three different types of Native American mounds.

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

A 400-foot-tall tall map of Chicago makes this once-ignored building stand out.

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

Museum dedicated to the art of cutting and polishing stones.

Half-sized replica of the Leaning Tower of Pisa built to honor Galileo.

You have to love a museum with a truly dedicated focus. A focus on Superman, for example.

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

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

The ancient tomb acts as a calendar that keeps perfect time.

The modern birthplace of Irish freedom.

A monument stands at one of the starting lines of the Trans-Canada Highway, formerly the longest uninterrupted highway in the world.

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

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

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

The Old Courthouse takes visitors on a captivating trip through St. Louis' timeline.

Speak to a companion on the other side of the room loud and clear through this architectural anomaly.

An extraordinarily ornate museum in San Diego holds wondrous anthropological treasures.

America's most famous piece of self-built architecture.