Berthed at the Charlestown Navy Yard in Boston, "Old Ironsides" is the oldest commissioned warship still afloat.

Mediterranean castle on a tiny Turkish island.

Islanders once used this dramatic, otherworldly landscape to hide their cattle from Viking raiders.

Ancient cliffs resembling a kilt on Scotland’s second-largest island emit an entrancing sound.

These fantastically named natural pools look like something out of a Scottish myth.

The ruins of this gorgeous clifftop castle look like something from a fantasy novel.

These official units of measurement—including chains and perches—lie hidden beneath tourists' feet in a popular London hub.

This massive collection of British military artifacts includes the heartbreaking personal letters of the men in the trenches of WWI.

Kings Cross Station pays tribute to its role in Britain's best-selling book series.

A charming 17th-century alley is lined with secondhand bookstores and antiquarian shops.

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

The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

Two stone columns flank the grand Venice square, but there were supposed to be three.

Go inside to really appreciate this 500-year-old technological masterpiece.

Dedicated to the American general whose reply to a German demand for surrender was simply "Nuts!"

A bust of Franz Kafka spins in pieces, reflecting the writer's inner torment.

Macabre astrological automaton clock dating to the late 1400s.

This modern French ossuary contains the jumbled bones of 130,000 WWI soldiers.

This museum in the small German city offers a unique glimpse into World War II history.

A team of concrete athletes stands in the middle of a traffic circle.

A unique look into the bowels of a century-old funicular.

Lines on the pillar of Heidelberg's Karl-Theodor Bridge record the dramatic heights of past floods.

In this German city center, the streets have no names.

Celebrating the works of a beloved Italian actor, known for such cult films as 'They Call Me Trinity' and 'Watch Out, We’re Mad!'