This unusual piece of Renaissance art depicting the bodily horror of crucifixion and skin disease may have been inspired by fungus-induced hallucinations.

The remains of this castle, known as the Witch’s Eye, watch over the Thur Valley.

A mud statue stands in the dark tunnels, seeming to hold up the weight of the city above.

The industrial architecture honors the laborers who brought the Exposition Universelle of 1900 to life.

This structure atop a craggy cliff in one of the most beautiful parks in Paris boasts an unbeatable view.

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

The tradition of open-air secondhand and antiquarian bookselling in Paris dates back to the Renaissance.

The curious underground history of keeping Paris clean.

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

Exquisite wall sculptures carved in secret by an early quarryman in an obscure corner of the Paris Catacombs.

A scandalous Art Nouveau collaboration that set Paris all atwitter at the turn of the century.

A haunting collection of the vanished and disappearing natural world.

Notorious artist squat renovated into legal studios.

This series of Baroque passageways in Vienna's cultural center mix old architecture with modern art.

A neo-Gothic church built to thank God for saving the Emperor of Austria from an assassination.

Inside the corridors of this flea market, visitors are sure to find some obscure and odd treasures.

Vienna's giant wonder wheel had a starring role in one of the greatest noir movies of all time.

This cubist Vienna church building looks like some sort of alien stonehenge.

Op-art architecture designed for happiness.

Dine amidst exotic plants at this former royal greenhouse.

A tropical paradise just a short trip from the opera house is filled with beautiful winged creatures.

The final resting place for the remains of 143 Habsburg royalty.

There has been an astronomical clock on this spot since the 14th century.

Wander among free-roaming storks at the sanctuary that helped save them from local extinction.