Enchanting cave with a river crashing through the roof.

A dangling church built over a Colombian gorge.

This picturesque mansion has gone from opulent ruin to nature museum.

Wax models of disease and deformity are on display at this German medical museum.

A tropical paradise just a short trip from the opera house is filled with beautiful winged creatures.

The bomb-ravaged remains of of a colossal Neptune.

The Andean town where every single building is decorated with a brightly colored frieze.

Ordinary art transforms to extraordinary thanks to locals' quirky sense of humor.

Original cabaret handbills, posters, and feline artwork are a purrfect highlight of the Museum of Montmartre.

The spiral staircase hidden inside this giant Parisian column was likely built for Catherine de Medici's astrologer.

Saintly bones pressed into a wax effigy of a Catholic superstar.

A modern-day Lascaux cave underneath Paris.

A font of vintage porn on the silver screen.

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.

A unrivaled and rather horrifying collection of wax dermatological models.

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

The largest medical and anatomical collection in France lies hidden from the public.

A mechanized clock where a man fights off a dragon, crab, and rooster.

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

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

A series of caves under Castle Hill that once held the prisoner Vlad Tepes, better known as Count Dracula.

A forgotten graveyard lost in the tangles of an overgrown garden.

Legions of Roman soldiers bathed in this ancient spa complex under a Budapest transit station.