A cave dwelling that was started by the Celts, expanded by monks, and finished by knights.

An icy lake tucked among jaw-dropping alpine panoramas.

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

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

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

This French ghost town from World War II has been left as a memorial to German atrocities during World War II.

This whimsical castle of grottoes was the labor of love of a French postman, and one of the greatest achievements of outsider architecture.

Walk upon the mementos of the dead in this Parisian courtyard paved with medieval tombstones.

A short distance from the Eiffel Tower is the final resting place of several of the city’s more well-known and interesting characters.

The oldest and smallest cemetery in Paris is only open to the public twice a year.

A Parisian exterminator's shop whose storefront displays stuffed rats hanging from traps.

How did a French journalist’s grave become the sexiest statue in the cemetery?

A surrealist timepiece by the artist of melting clocks.

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

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

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

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

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

Abandoned railway line circling the city of Paris.

Locals say the stone that marks the spot where the gallows once stood can lead you astray.

Tall columns of volcanic basalt make up this improbable-seeming rock formation.

This ruined castle perched atop a rocky peak is a great place for a hike.

A mesmerizing landscape of 18th-century cellars carved out of the land.

The 14th-century ruins are said to contain healing powers.