The oldest residential street in Europe also features an optical illusion.

This astronomical clock is the second oldest in England.

Inside this magnificent 12th-century church is one of the finest carved wagon-roofs in all of England.

This ingenious engineering solution was built to stop the "theft" of canal water.

Besieged by war, this castle ruin has crumbled into a peaceful picnic spot.

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

The subterranean "lake" below the Paris opera house inspired the Phantom of the Opera's lair.

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.

19th century pendulum and a clock restored by a rogue group of guerilla artists.

This statue was given to France by the United States to commemorate the centennial of the French Revolution.

The very center of Paris is surrounded by a bevy of strange good luck rituals.

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

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.

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.

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

Abandoned railway line circling the city of Paris.

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

This Romanian village may have been drowned, but it is long from forgotten.

This memorial to the victims of the Romanian Revolution of 1989 is often compared to a potato on a skewer.

17th century palace once a meeting place for politicians.

Home of the first female Hungarian poet, where her secret writing lay hidden for over a century.