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

A Jenga-style cylindrical tower of books that appears to go on forever.

Macabre astrological automaton clock dating to the late 1400s.

The Renaissance-era courthouse is a relic from the fortified town's centuries of Venetian rule.

Longest fortress system anywhere in Europe.

A musical instrument played by the sea.

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

A curious cave church carved into the face of a cliff.

These historic defenses ensured the city within would survive hundreds of years of occupations, sieges, and invasions.

This 18th-century sundial was designed to calculate the date of Easter each year.

The huge golden reliquary of a testicle-smashing saint.

This triumphal arch celebrating the Sun King's conquest of Lille is a masterpiece of military architecture.

A copy of the Statue of Liberty greets visitors to the birthplace of Auguste Bartholdi.

Walk through living pictures and music in the Cathedral of Images.

This medieval tower is all that remains of the castle where Joan of Arc was held before being burned at the stake.

One of the largest ochre quarries in the world, hidden in a limestone landscape.

This bridge was constructed from the rubble of the infamous Bastille.

A chapel on a volcanic core, marking the end of a successful journey.

The world's tallest bridge is also possibly the most elegant.

This stunning French estate was so lavish that it landed its original owner in jail for the rest of his life.

This ancient Roman bridge and aqueduct still stands as a wonder of classical construction.

This modern French ossuary contains the jumbled bones of 130,000 WWI soldiers.

The water-powered carriages are long gone, but for over a century this funicular railway has been the fastest route to the highest point in Paris.

Twelve grave-faced marble angels guard the emperor's tomb at Les Invalides.