In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

The walls of America's oldest masonry fort famously "swallowed" cannonballs.

The famous boat that once ferried Bogart and Hepburn still floats in Key Largo after being abandoned for years.

A luxurious 1880s hotel with its fair share of Tiffany stained glass, Edison electricity, and of course, ghosts.

The former home of the Nobel Prize-winning American writer is now home to dozens of six-toed cats.

The celebrated eyesore created by starry-eyed sweethearts.

Twelve grave-faced marble angels guard the emperor's tomb at Les Invalides.

France's most famous cemetery, with some of its most curious tombs.

A mysterious shape catches the eye in this 16th-century painting.

The "lost friend” is the most famous of the six moai statues that were removed from Easter Island.

Hear the quietest sound from across the dome.

The perfectly preserved underground rooms where Churchill plotted the war against Germany.

The modern birthplace of Irish freedom.

A sacred well steeped in Pagan roots on the West Coast of Ireland.

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

The gorgeous library at Trinity College is home to remarkable treasures of Irish identity.

The home of the first American-born saint is one of the only curved buildings in New York.

This historic address is home to the beloved ball and is an almost totally empty building among the most expensive real estate in the world.

Visit the monolithic tomb of America's most famous general.

This mosaic dedicated to John Lennon was tended for years by a Beatles super-fan.

This cemetery has graves dating back to the 17th century, including the city's oldest carved tombstone and an ominous cryptogram.

Whisper secrets in a busy station only to be heard on the other side of this acoustic arch.

Elevated freight railway turned wildly successful urban park.

Largest tulip festival in America, includes fireworks, a parade, and a carnival.