An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

This former “ante-chamber to the guillotine” has been refurbished to illustrate the brutal history of French justice.

Medieval museum built over Roman baths that features famous tapestries of a lady and a unicorn.

A Parisian cemetery where the elite and artistic are interred beneath an eccentric collection of tombs.

A museum on the history of Paris, including a set of Napoleon's toiletries, Proust's room, and relics of the Revolution.

The celebrated eyesore created by starry-eyed sweethearts.

A counter-culture bookstore like no other hides in plain sight in the streets of Paris.

France's most famous cemetery, with some of its most curious tombs.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

The remains of Crystal Palace Great Exhibition of 1851.

Abstract dinosaur models in London.

The underground sanctuary of a mysterious ancient cult.

Eighty million natural history specimens call this gargantuan museum home.

This small museum in a former church crypt contains artifacts of the Elephant Man, Jack the Ripper and Florence Nightingale.

One part local history, 99 parts gruesome haunted house.

Scattered throughout London are ancient remnants of the city's former bounding wall.

A Museum of Psychiatry in a still-operating mental institution.

This fairytale castle was built as a show of power but was nearly torn down thanks to its history of torture.

A magical and peaceful ruined Cistercian abbey in what is now southern Belgium.

Each spring, a dreamlike carpet of bluebells overtakes the forest floor.

A pilgrimage site where people ask Saint Dymphna to watch over those who are not of sound mind.

Three floors of musical instruments coming from all corners of the world and hundreds of years of musical history.

A little sculpture with a large wardrobe.

From Tintin to the Smurfs, Europe's greatest graphic icons are celebrated in a grand Art Noveau gallery.