A lone cannonball remains lodged in the walls of the Hotel de Sens as a sober reminder of a revolution.

BDSM, 1930s Style.

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

This surreal statue brings a famous French novel about a supernatural cad to arresting life.

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

A series of abstract, silly sculptures represent the works of a great modern classical composer.

This noble mash-up in eastern Luxembourg is part Medieval, part Renaissance, all castle.

An expansive complex of subterranean tunnels is all that remains of one of Europe's most formidable medieval fortresses.

This Greek temple, open only an hour a day, was the site of a war of tastes between an architect and an artist.

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

Housing the groundbreaking maps and globes of Gerard Mercator.

Most prolific publishing house in the 1600s open to the public.

An open-air sewer system that was covered piece-by-piece over 300 years.

Rare wooden escalators lead deep down into an otherwise staggeringly monotonous tiled tunnel.

This collection of over 50 murals celebrates Brussels' rich history as the self-proclaimed home of the "comic strip."

When you're a great Russian Tsar, even your vomit gets a statue.

Theme park featuring miniature replicas of European monuments.

Climb inside an iron crystal magnified 165 billion times its normal size.

A fantastical 13th-century fortification sandwiched by a modern hotel in central Brussels.

Statue commemorating the use of ether in anesthesia.

A men’s restroom became a sandwich shop.

One woman’s obsession gave birth to this lovely oddity at the Boston Public Library.

This memorial honors those who served on Gallops Island Radio Training Station during the second World War.

The headquarters of one of the world’s longest-running humor magazines bears a noticeable resemblance to a head wearing a Prussian helmet.