A natural arch carved by a river gave its name to the so-called "Cave of Forgotten Dreams."

The fantastic architectural models of a French traveler.

The floorboard scrawling of a tragic madman is on public display outside a Paris hospital, much to the dismay of its opponents.

These quaint French houses dangle precariously over a precipice.

A well-preserved medieval village nested on a rocky outcrop and surrounded by a network of cliffs, natural bridges and canyons.

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

Monsters and miniatures are held in equal esteem at this wondrous museum.

Two small chapels housed inside an ancient tree.

A beautiful and classically designed villa, with an hourly infestation of monsters.

Rumors of the occult haunt this upscale 1920s hotel.

A 19th-century British industrialist built this Louis XIII–inspired chateau for his homesick French wife.

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

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

Claude Monet was baptized in this lavishly ornate Paris church.

Museum on French naval history, with magnificent figureheads, a historic diving suit, and a boat used by Napoleon.

The only remaining collection of flayed figures made by French "madman" Honoré Fragonard.

For hundreds of years, automatons moving to metallic music have been marking the passage of time.

This Paris art space celebrates the creativity and ingenuity that springs from abject poverty, especially in Africa.

This museum in a Paris apartment gives a unique look at the iconic French singer's life.

The largest underground church in Europe.

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

Historic medieval fortified city in southwest France.

The mental institution where Van Gogh created some of his most famous work now allows guests to walk in the artist's footsteps.

An off-the-beaten-path boutique stuffed with an eclectic collection of upcycled goods.