An eerie, little-known Neapolitan museum filled with preserved human remains.

In a city that boasts four separate inclined cable railways, this is one of the busiest funicular lines in the world.

Dug as a secret royal escape route, the tunnel became a wartime bomb shelter and dumping ground for vintage cars.

This ancient Roman prison is decorated with an upside-down cross not as blasphemy but as saintly tribute.

At the crypt of St. Mary of Eulogies and the Dead you are left alone to ponder mortality among piles of skulls.

The underground sanctuary of a mysterious ancient cult.

An extraordinary collection of 18th century anatomical waxworks.

This museum is rotten with a century of wax medical deformities.

The oldest operating pharmacy in the world features 800-year-old recipes.

Nestled on the banks of a river in Nuremberg is a small museum that was once home of the city's official executioner.

The largest ice cave in the world is thought to be the entrance to hell according to Austrian legend.

The walls of this medieval church are covered with perfectly preserved frescos, including a pristine example of the Dance of Death.

This massive subterranean fissure is known as the "underground Grand Canyon."

A cemetery for Slovenian notables also serves as a popular recreation space.

The townhouse where the "Blood Countess" Elizabeth Báthory started her murderous career.

This museum promotes informed contraception by documenting its often secret past.

A collection of anatomical samples from one of the first anthropologists to suggest that humans reached North America by crossing the Bering Strait.

Around 100,000 bodies are buried below the medieval headstones, many of which mark graves with multiple bodies stacked up to 12 deep.

Walk through Czech history in Prague's largest graveyard.

Two stunning 17th-century libraries and a cabinet of curiosities.

Beneath the impressive baroque cathedral that rises from the center of Berlin lies the largest collection of Prussian royals in the world.

A museum dedicated to the history of a terrifying secret police is now held in their former headquarters.

A tour of underground Berlin takes you through WWII air raid shelters and tunnels used to smuggle people out of East Germany.

This 22-floor tower's Skydeck offers panoramic views of Amsterdam.