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

The vast, legendary catacombs hold secrets much stranger than stacked bones.

A collection of noses tucked inside an art museum reveals how times have changed.

Opulence and fantasy collide in this royal chair which is supposedly made with unicorn horns.

Vortex-shaped aquarium hosts Europe's largest school of piranhas and other ocean creatures.

Copenhagen's celebrated theme park and gardens.

The idyllic island where the philosopher Jean-Jacques Rousseau spent “the happiest time of his life.”

150-year-old satirical tableaus made from stuffed frogs.

This is not only one of the oldest collections in Europe, but also possibly the most beautiful.

This memorial commemorating fallen Swiss Guards of the French Revolution has been called the saddest stone in the world.

This lovely little bridge hidden in a Switzerland gorge is essentially a fairytale.

This medieval cathedral houses stained-glass windows featuring saints and pretzels.

Twelve sweet, nutty, life-sized statues are housed in this second-story shrine to almond paste.

A steam powered train that runs on city streets.

This bakery and museum offers tours of the tastes and mythology of Aachen's signature spice biscuit—just don't ask for the recipe.

The narrowest street in the world is in danger of closing up entirely.

Flowers have mysteriously appeared on her effigy every day for the last 150 years.

A series of haunting wooden totems are hidden in the woods surrounding a German environmental center.

The birthplace of Karl Marx is now a museum dedicated to the communist revolutionary's life and work.

The first (but not only) upside-down house in Germany.

An engineering wonder at Pillnitz Castle protects a precious 230-year-old flowering shrub.

Originally envisioned by King Ludwig II to rival Versailles, Herrenchiemsee's "New Palace" remains half-gilded for lack of funds.

Thousands of tourists and residents in Cologne affix "love padlocks" on the Hohenzollernbrücke Bridge to symbolize their affections.

When a medieval fire claimed the original St. Stephen’s Cathedral, it sparked a pattern of unquenchable organ building.