This futuristic German spa allows visitors to float in a pool of salt water while zoning out to underwater techno.

An eerie, derelict amusement park in Berlin.

This statue honors one of Budapest's most beloved literary characters.

Extremely famous in his native country, this Cracovian painter is all but unknown beyond Polish borders.

This Polish cave has housed a dragon, a brothel, and an enduring legend.

Beneath Kraków Old Town's main square lies a hologram-filled medieval market vampire graveyard wonderland.

This supermarket offers shoppers a window into the past alongside their groceries.

A museum dedicated to one of Paris’s most famous residents, tucked into a corner of one of the city’s most famous squares.

Beggars were miraculously "cured" of their fake ailments when they returned home to this 17th century Paris slum each night.

An immersive projection art installation uses sound, scale, and light to take visitors inside classic works of art.

The curious underground history of keeping Paris clean.

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

A subterranean shelter remains intact under a busy Paris railway station.

The oldest stone house in Paris was built by its most famous alchemist.

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

Pitié-Salpêtrière was the dumping grounds for women who received the dreaded diagnosis of "hysterical."

The history of radiation is on safe display at the foot of a radiation science laboratory.

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

An extraordinary library and archive dedicated to the history of the Arctic and Antarctic poles.

"Purveyors of traditional sweets and vintage treats."

Since 1874, this macabre collection has developed into a museum devoted to Scotland Yard's mementos of dastardly deeds.

These docile dragons are ideal inhabitants for the conservatory greenhouses.

An archive of ceramic eggs painted to record clowns' personal makeup designs.

Tucked away in the Tower of London is the weapon once used to execute high-profile prisoners.