These secluded and abandoned anti-aircraft defenses have become one the most scenic viewpoints in Barcelona.

Gaze upon chocolate sculptures depicting everything from chariot races to Gaudí's famous church at this shrine to sweets.

This cemetery features modernist statues as strange as its name.

A beautiful but toxic fountain of mercury.

This semi-secret storybook hedge maze is also the oldest garden in the city.

The world’s narrowest house makes for an awkward, four-foot-wide living space.

A perfectly preserved hill village where the buildings are painted like white lace.

A subterranean shelter remains intact under a busy Paris railway station.

The spiral staircase hidden inside this giant Parisian column was likely built for Catherine de Medici's astrologer.

This little-known relic crypt holds stolen parts of a Roman Empress.

The first green space constructed on an elevated viaduct.

This Parisian café sticks almost exclusively to an ethos of reuse.

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

This Parisian fountain is a little bit fantasy and a little bit nightclub.

Where the high court feasted, frolicked, and high courtesans put their royal lovers' diamonds to the test.

The curious underground history of keeping Paris clean.

A grotto-like lodge decorated with gilded mosaics, rocks and a noisy waterfall was the setting for the most sumptuous pleasure house of 1900s Europe.

Egyptian Revival movie palace abandoned for decades and restored in 2013.

Indents in the pavement are all that remain from a grisly death machine in Paris.

Known as the "Dodo Manège," this carousel features a herd of animals that have disappeared—or may be gone soon.

Stroll through retro Paris while shopping for old postcards and discarded doll heads.

Behind the pink curtain, Au Bonheur du Jour, an art gallery of erotic archives.

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

Paris' linguistic guide to the international language of, yes, love.