The hidden lair of an alchemist rediscovered in a 2002 flood.

A Jenga-style cylindrical tower of books that appears to go on forever.

Macabre astrological automaton clock dating to the late 1400s.

The most visited, and possibly most controversial, museum in Germany.

Thousands of coffin-like pillars make up this controversial Holocaust memorial.

A memorial in the Tiergarten is a reminder of the suffering inflicted on homosexuals by the Nazi regime.

Cat art as far as the eye can see.

This unattributed sculpture in Amsterdam is hiding in plain sight.

The world's only museum devoted to the wonders of fluorescence.

A floating cat sanctuary on an Amsterdam canal.

A Dutch passageway's artistic, aquatic-themed makeover pays tribute to the capital city's famed waterways.

The preserved left hand of a saint once known as "the Pearl of York."

Reputedly based on the tomb of Jesus Christ, this crypt is the oldest surviving structure of any cathedral in England.

At 22 feet tall, these Bronze Age monoliths are some of the tallest standing stones in the United Kingdom.

A 600-year-old mini shrine guarded by a sword-wielding knight hides in a crumbling cliff face.

Once thought to be the mysterious work of a witchy prophetess, a well with unusual properties turns objects into "stone".

Hidden in the woods behind this English estate lies a Victorian pet cemetery.

This Victorian graveyard in Leeds is a macabre collection of beautiful tombs and memorials.

The photographs of "fairies" that fooled much of the world (including the creator of Sherlock Homes) were taken at this English stream.

This Gothic Revival castle used as a shooting location for "The Secret Garden" and other films.

In the middle of a barren moorland, the remnants of a lost British Space Age stand like a 20th-century Stonehenge.