A museum which takes visitors to the côté obscure of Paris.

A beautiful but toxic fountain of mercury.

Portugal's National Pantheon has a history of curses, collapses and financial problems.

This once-forgotten oasis in the middle of Lisbon was first created over a century ago quite by accident.

This unique architectural wonder is also tied to one of the 20th-century's most renowned writers.

Tucked away inside this concrete building is a church and its grand display of brutalist architecture.

One of the smallest bookstores on the planet.

Catering to broken dolls for almost 200 years, this repair shop is now a charnel house of doll parts.

The world's oldest bookshop still in operation.

The bizarre headgear looks like it was made for a fool, not a king.

The former 1920s mansion of a prominent Catalan developer was used as the Soviet Embassy during the Spanish Civil War, and there is still a bunker below the garden.

This lovely ancestral home inspired the author D.H. Lawrence, and features a tunnel made out of a living willow.

A secret meeting in this small cottage changed the course of British history.

A brick foundation and piles of listing building materials are all that remains of this World War II POW camp.

Long-secret natural history museum, featuring the skull of a "Terror Bird."

Order “Proletariat’s Cutlet” at this communist-themed restaurant allegedly once visited by Lenin.

Once home to some 250,000 volumes and priceless art artifacts, this Polish estate was a target of bombing during World War II.

A statue honors the children who fought Nazis in Poland.

This hidden collection of everyday objects illustrates life within communist Poland.

One of the world's largest collections of medieval religious art.

Austria's ultra-modern art museum looks like Cthulhu's giant alien heart.

Fantastic stories on a miniature railroad.

Double spiral staircases are not unheard of, but they are very rare.

The world's largest historic armory was established by independent citizens to defend themselves from the wars of larger forces.