Art and a pun, all in one.

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

A surreal museum of extraordinary industrial objects.

A whimsical and twisted animatronic monster tour beneath the streets of Berlin.

A fairy tale castle in modern Rome.

An alchemist's "magic door" stands in the middle of a Roman park.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

The only "Egyptian" pyramid in Europe and the legendary tomb of Remus.

A Nesting Doll of Churches.

One of several skulls claiming to belong to the beheaded St. John the Baptist is on display at this Roman church.

Architectural monsters are devouring this palace's every door and window.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

At the crypt of St. Mary of Eulogies and the Dead you are left alone to ponder mortality among piles of skulls.

Rome's semi-secret peephole vista is also a former Crusader stronghold.

A mysterious chasm in the heart of the ancient Roman Forum, the Lacus Curtius was once believed to be a gateway to hell.

The skull of the patron saint of lovers lies in the Basilica di Santa Maria in Cosmedin—maybe.

The underground sanctuary of a mysterious ancient cult.

Weird wax anatomical models reside here, as do other anatomical specimens.

A surrealist timepiece by the artist of melting clocks.

Walk upon the mementos of the dead in this Parisian courtyard paved with medieval tombstones.

The oldest stone house in Paris was built by its most famous alchemist.

A mechanized clock where a man fights off a dragon, crab, and rooster.

Notorious artist squat renovated into legal studios.

A unique underground structure dating back to the 1st century BC.