This semi-secret storybook hedge maze is also the oldest garden in the city.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

An ancient Greek monument and a Byzantine church coexist inside this cave.

These caves secretly held national treasures during World War II.

Heralded as the world's first theater, these ruins are often overlooked as they reside in the shadows of the Acropolis.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

This monumental fountain has moved around the city multiple times.

A rococo room covered entirely in porcelain originally constructed for another royal residence.

The remains of the left arm of the levitating philosopher-saint are kept in a 13th-century Neapolitan basilica.

An unusual "skull with ears" sits in the crypt of this small church tucked away at the end of a narrow alley.

This magical-looking island is notorious for the misfortunes suffered by its owners.

A labyrinth of ancient tunnels hidden below the city holds the ruins of 2,500 years of history.

The celebrated eyesore created by starry-eyed sweethearts.

A poem by Arthur Rimbaud is inscribed on the wall of a street that, while it is only one block long, plays a key role in multiple novels.

The oldest continuously operating mint in the world that has been making coins since the 9th-century.

Beggars were miraculously "cured" of their fake ailments when they returned home to this 17th century Paris slum each night.

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

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

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

France's national museum of scientific and industrial instruments.

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

A counter-culture bookstore like no other hides in plain sight in the streets of Paris.

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

One of the oldest medical collections in Europe focusing on rare surgical instruments.