This curious, round temple is the oldest still-standing marble building in Rome.

This ancient market is often referred to as the oldest shopping mall in the world.

This large, circular tomb is the final resting place of the first emperor of Rome.

This beautiful park on the outskirts of Rome protects the ruins of two colossal ancient aqueducts.

An alchemist's “magic door” stands in the middle of a Roman park.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

A gruesome combat between a hunter and a furious momma bear.

For more than a century, revolutionary graffiti has marked the wall of a Parisian church.

The remains of the medieval wall that once surrounded Paris with ties to the construction of the Louvre.

The tombstone of an unfortunate explorer who disappeared in the Paris Catacombs.

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

An iconic and eccentric bar for "Manouche" Jazz music keeps expanding its space—and its influence.

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

This frog-themed restaurant was frequented by Picasso, Saint-Exupéry, and more.

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

Berlin's natural history museum houses the world's largest mounted dinosaur and the late beloved polar bear Knut.

Executions were once held near this beautiful 18th-century fountain.

A charming flea market shop dedicated to retrofuturistic apparati.

A melancholy jester sits on the grave of a famous 20th-century ballet dancer and choreographer.

The heaviest gold coin ever minted.

Collection of antique taxidermy and natural specimens, near one of Paris's oldest flea markets.

What looks like a normal building is really a hollow facade hiding a subway vent.

In the best of all possible worlds, everyone will get a chance to see this statue in which Voltaire's heart is interred.

It's just another skyscraper, but it's shaped like '90s cell phone.