The iconic Chicago sculpture hides a beautiful and easily overlooked plaque on the backside.

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

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

An outdoor urban gallery of large-scale artworks by the world's most influential street artists.

Home to a protest movement, a bombing, and a dramatic change in labor history.

The final resting place of Harriet Tubman and other famous historical figures.

What remains of the simple red brick chapel where the women's rights movement began.

Every hour the doors open to reenact the legend of the heroic mayor who saved his town by drinking a gallon of wine.

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

Horrifically creative torture devices and shame punishments line the walls of this chilling museum.

The prototype for all Nazi concentration camps.

Enter the cabin of a life-sized Hindenburg replica.

The fairy tale castle of the “fairy-tale king,” this was also the inspiration for Disney’s “Sleeping Beauty.”

Amsterdam's narrowest house facade is a monument to 17th-century tax evasion.

These wire animal sculptures commemorate the exotic inhabitants that once called the Tower of London home.

The watery entrance for condemned prisoners heading to the Tower of London is still visible along the Thames.

Six ravens are kept captive (but well-fed) at the Tower of London to prevent the fall of the Crown.

This statue was given to France by the United States to commemorate the centennial of the French Revolution.

This 19th-century building inadvertently preserved the handprints of its builders within its walls.

Mile-long cave system near Great Smoky Mountains.

This fountain was commissioned by a mother grieving over her son's passing.

One of the largest-ever mental hospitals now sits abandoned, surrounded by 25,000 unmarked graves.

The only working large-scale tea plantation in the United States.

A once-groundbreaking power plant turned into a hotel and mini-museum of archeological and geological wonders.