This city square is home to Amsterdam's oldest church and a statue honoring Dutch sex workers.

Amsterdam's Red Light District leaves little to the imagination.

Island ghost town detailing Flagler's folly in building the Overseas Railroad.

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

A monument celebrating the idea of reaching inaccessible places.

His music once banned in Communist Cuba, John Lennon is now immortalized in bronze by Castro, who considers Lennon a "fellow dreamer."

The once-abandoned 140-year-old hotel used in the movie "In Dreams."

"X" marks the spot of an echo chamber in the middle of a plaza.

South Carolina's last remaining slavery auction house is now a museum devoted to its own tragic history.

Paths are maintained, but trees have taken over plots.

The largest university building in the West is a gothic masterpiece containing dozens of theme rooms based on different countries.

Mysteriously stacked storefront paths give this medieval British town an iconic style like none other.

The quiet field that inspired one of the most famous songs of all time.

Lewis Carroll's White Rabbit or something else altogether?

One of the few standing Roman lighthouses and a labyrinth of tunnels are a couple of the secrets at this historic castle.

Tiny castle in the middle of the Rhine made you pay to pass.

The prototype for all Nazi concentration camps.

The footprint of a frustrated devil in Munich's Cathedral.

Daily jousts and dancing barrel makers in Munich's mechanical clock.

Go surfing on this urban wave, "hacked" by local surfers.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

Where commuters walk through remnants of an ancient Greek necropolis.

A 2,000-year-old computer demonstrates remarkable engineering and astronomical precision.

An organ located deep within a cave, whose "pipes" are the geological features of the cave itself.