The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

This banal Parisian entranceway is not what it seems.

This former “ante-chamber to the guillotine” has been refurbished to illustrate the brutal history of French justice.

This frog-themed restaurant was frequented by Picasso, Saint-Exupéry, and more.

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

A haunting collection of the vanished and disappearing natural world.

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

The water-powered carriages are long gone, but for over a century this funicular railway has been the fastest route to the highest point in Paris.

Statue of death tucked in the University of Medicine courtyard.

This Parisian café sticks almost exclusively to an ethos of reuse.

This Parisian fountain is a little bit fantasy and a little bit nightclub.

This massive library holds what was once the largest book collection in the world.

A statue of the second-tallest Dutchman in history.

The largest 19th century panorama in the world still in-situ.

Hidden within a Netherlands crater is a stone bed that lets those who lie in it see the sky as a curved surface.

Cat art as far as the eye can see.

A ghost town now swarming with dozens of prairie dogs.

A section of the long chain that blocked enemy ships from entering Constantinople.

A marvel of Byzantine engineering under the streets of Istanbul.

A magical place that lets you play in and explore the world of Studio Ghibli.

Museum celebrating the ocean, with the largest wunderkammer dedicated to sea exploration.

One of the tallest buildings in Iceland, and perhaps, the most visually impressive.

An eccentric garden of sculptures crafted in India decorate an Irish green space dedicated to Alan Turing.

Monasteries on rock pillars, once accessible only by frayed ropes.