A saintly relic hidden in a Prague church basement.

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

This overlooked street light once served as a KGB dead letter box.

A mysterious pair of mice eating a piece of cheese is London's smallest public sculpture.

One part local history, 99 parts gruesome haunted house.

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.

This Venice bookstore has resigned itself to constant flooding by keeping its books in bathtubs and boats.

This 14th century wine cellar is home to the oldest barrel-stored wine in the world.

One of the best-preserved medieval streets in Europe.

After it was swallowed by a Georgian mansion, this medieval castle remained forgotten for centuries.

The modern birthplace of Irish freedom.

The block of aged dairy is probably still edible after 2,300 years in a peat bog.

The house where the writer spent his formative years.

The Grand Lodge of Ireland is one of the oldest in the world, full of fantastical, elaborately themed rooms.

The comedy and tragedy of Oscar Wilde is preserved in a Dublin park, captured in a sculpture of colorful stone.

Anonymously sculpted and donated, these sculptures made from poetry books and pages are sprinkled around the city.

An artistic interpretation of the history of a Scottish park, combining poetry with anthropomorphic animals.

Touching this 18th-century Scottish philosopher’s toe allegedly conjures good fortune.

A six-ton wedding present for the King of the Scots.

This repurposed church offers a more literal way to get closer to the heavens.

Near the former site of numerous witch burnings, this lavish Edinburgh mainstay pays homage to Scotland's brutal history.

A British Commonwealth cemetery in the heart of Milan, with 421 allied soldiers died during World War II.

A flamboyant five-story building in Bulgaria resembles a crawling snail.

Skulls from the plague of 1656 and World War II bombings are united by a cult dedicated to caring for the ancient dead.