Perhaps the most spectacular grotto along the Algarve coastline.

This small chapel is built of human bones and decorated with a golden skeleton.

This secluded walkway overlooks a magnificently wild London green space.

Western Europe's only representation of a Roman goddess still in its original location sits in an unassuming park.

A charming flea market shop dedicated to retrofuturistic apparati.

An antique curios dealer and hybrid taxidermist.

Inside a former cabaret, seven floors of erotic art.

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

Weird wax anatomical models reside here, as do other anatomical specimens.

The narrowest street in Paris.

This structure atop a craggy cliff in one of the most beautiful parks in Paris boasts an unbeatable view.

Stripes of human ashes cover a back lawn in the most sought-after burial grounds in Paris.

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

The industrial architecture honors the laborers who brought the Exposition Universelle of 1900 to life.

An unusual number plate signifies the building's saucy past.

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

One of the oldest masonic museums in Paris.

Architect Le Corbusier built his friend a cubist house to match his impressive collection of cubist art.

This innocuous-seeming building is actually the remnant of a major wartime brothel.

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

This off-limits room in the National Library of France is home to a system of pneumatic tubes, once used to bring books to readers.

Skeletons, medical artifacts, and other obscure and precious treasures all displayed in a wooden pharmacist's cabinet.

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

Hidden away in a modern library are the remains of one of the 18th century's most celebrated wunderkammers.