An expansive complex of subterranean tunnels is all that remains of one of Europe's most formidable medieval fortresses.

The last bastion of Roman presence north of the Alps looms over a German town.

The birthplace of Karl Marx is now a museum dedicated to the communist revolutionary's life and work.

This grand gothic brewery has been pumping out suds for over a hundred years.

Was there a small "backpack nuke" hidden in the attic? JFK apparently thought so.

Built in 1945, this historic train station has a new lease on life with its baggage area serving as an event space.

The rooster who crossed the road lives on forever in Takoma Park, Maryland.

The last holdout of a pre-Civil War rebel who took the matter of slavery into his own hands.

Thousands of tiny squares in different colors make up this piece of street art.

The largest earthwork effigy in the world.

The plants form a living library and laboratory for researchers and students at Michigan State University.

This mechanical wonder towers above a river in Michigan's capital city.

Four glass boxes hover over 1,000 feet in the air to give visitors an unparalleled view of Chicago.

This historic hotel invented the chocolate brownie.

Once at the center of U.S. finance, the historic Trading Room was meticulously recreated piece by piece and rebuilt in the Art Institute.

The palatial McDonald's that inspired Wesley Willis.

Roses and other fascinating flora fill this garden built to commemorate Britain's immortal Bard.

Less a museum than a bizarre fantasy world created by artists and engineers.

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

The world's longest known cave system.

The home used in just a few seconds of film that came to define the setting of a hit sitcom.

This mysterious hill seems to pull objects uphill.

For over 100 years, this Indiana town has had a tree growing out the top of the local courthouse.

The farm where one of America's greatest leaders was raised is now a well-appointed landmark.