Chicago’s incendiary role in the labor movement.

Where Agatha Christie mysteriously disappeared in 1926.

The ruins of an ancient stadium that hosted gripping chariot and horse races.

On the Hudson resides one of the largest clocks in the world.

The competition: breathe deeply as long as you can.

Ancient serpentine sacrifice holder that has stood the test of time.

America's largest man-made forest was planted in an effort to bring back the past.

This subtle Berkeley paving stone actually marks off a lawless tube of air that extends into space.

A "miracle" that seems to produce more holy fistfights than holy revelations.

A derelict bit of infrastructure from the canal that once ran through D.C. is landlocked in the heart of the city.

A constellation of golden cobblestones shows the names of local children born under a full moon.

A brutalist gem towering over the heart of Milan.

Chicago's Navy Pier on Lake Michigan was a training hub for aircraft carrier pilots during WWII.

This historic Boston building has gone from personal estate to porn theater and back again.

The remnants of the base where US Army troops learned how to fight in extreme conditions.

Spanish architects used seized Muslim gravestones to rebuild parts of the fortress.

From Ancient Rome to WWII, Neupfarrplatz has over 2,000 years of history underneath its main square.

This magnificent castle grew from a small Moorish fortress, and reportedly inspired two iconic Disney castles.

On Gellért Hill, this statue depicts the tragic tale of lovers divided by the Danube.

This postmodern apartment block was designed to be a vertical neighborhood.

An early life spent in this "Old Kentucky Home" inspired the writings of North Carolina's most famous novelist.

A simple but powerful tribute to the 20 victims of the 1692 witch trials.

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

A focal point of in Denver’s skyline for over a century, inspired by a Venetian basilica.