A 16th-century fountain marks the site of a lost medieval cemetery once filled with mass graves.

Remains of Roman amphitheater hidden in a sleepy quarter of Paris.

This structure atop a craggy cliff in one of the most beautiful parks in Paris boasts an unbeatable view.

Natural history museum celebrating biodiversity with a parade of taxidermy animals.

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

The narrowest street in Paris.

The tradition of open-air secondhand and antiquarian bookselling in Paris dates back to the Renaissance.

The curious underground history of keeping Paris clean.

A majestic lion statue guards this Parisian botanical garden, and feeds on an unsettling item.

The first green space constructed on an elevated viaduct.

Known as the "Dodo Manège," this carousel features a herd of animals that have disappeared—or may be gone soon.

The ruins of a Duke's bucolic dream, where camels once roamed alongside "Dutch" windmills and faux-Italian vineyards.

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

France's national museum of scientific and industrial instruments.

This museum houses an imposing skeleton army comprised of creatures great and small.

High atop the Eiffel Tower is a small apartment built exclusively to entertain the science elite and make the rest of Paris jealous.

A scandalous Art Nouveau collaboration that set Paris all atwitter at the turn of the century.

Notorious artist squat renovated into legal studios.

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

At this 16th-century monastery in rural Bulgaria, visitors can also spend the night.

A flamboyant five-story building in Bulgaria resembles a crawling snail.

This scale model of our solar system hid in plain sight for years before a physics team sought out all the planets.

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

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