The housing complex served as an anti-fascist fortress during the Austrian Civil War.

Vienna's diversity-themed traffic lights were inspired by the Eurovision Song Contest.

Giant WWII fortresses that fired 8,000 rounds a minute, now home to thousands of pigeons.

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

This off-limits room in the National Library of France is home to a system of pneumatic tubes, once used to bring books to readers.

A Parisian exterminator's shop whose storefront displays stuffed rats hanging from traps.

This life-size replica of the Statue of Liberty's flame is also a tribute to Princess Diana by default.

One of the last umbrella repair shops in Paris upholds the nostalgic art of umbrella making.

In the best of all possible worlds, everyone will get a chance to see this statue in which Voltaire's heart is interred.

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

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

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

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

This charming cobbled backstreet is the most Instagramable street in Paris, much to the residents' annoyance.

A horde of stray cats rule in this secluded Parisian cemetery under a bridge.

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

This massive library holds what was once the largest book collection in the world.

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

A domino effect created with Britain’s iconic telephone boxes.

Legend has it that seven Anglo-Saxon kings were coronated on this stone, located in the appropriately-named town of Kingston.

This Underground station has been a popular filming location for decades, even before it closed.

The famous polar explorer stands outside the Royal Geographical Society's headquarters.

A mysterious shape catches the eye in this 16th-century painting.

The sumptuous ceiling was one of the last things Charles I saw before his execution.