A contemporary art installation housed within a Gothic cathedral.

The Cambridge pub where Francis Crick announced that he and James Watson had discovered the DNA double-helix.

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

Visitors dating back to the 1600s carved their marks in the stones of the iconic tower.

Daily jousts and dancing barrel makers in Munich's mechanical clock.

This one-time health resort was used by aristocrats around the world.

A surreal statue honoring Prague's favorite literary son.

This tipsy office building in downtown Prague was originally called “Fred and Ginger.”

Macabre astrological automaton clock dating to the late 1400s.

A museum dedicated to a secret military hospital hidden beneath a castle in Budapest.

From Austrians to Nazis to Soviets, this historic Budapest fortress has a history as complex as the city itself.

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

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

Baroque celebration of the end of the Great Plague of Vienna.

Built to give thanks for the passing of a plague epidemic, this cathedral is a one-of-a-kind architectural hybrid.

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

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

A Parisian cemetery where the elite and artistic are interred beneath an eccentric collection of tombs.

This modest marker near Notre Dame identifies the very center of Paris.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

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

Notorious artist squat renovated into legal studios.

A mysterious plaque to the even more mysterious "Fr. Pat Noise," killed in "suspicious circumstances."

A statue in the center of Dublin dedicated to one of their favorite sons of rock & roll.