This private skyway is filled with art and was expanded explicitly so that Hitler could appreciate a river.

The famous sculptor left his mark on this Italian wall in an internationally protected example of street art.

Over 50 exquisite hand-painted Renaissance maps decorate a Medici storage room.

The doodles of a genius line the walls of a secret room under the Medici Chapel, where they were hidden for nearly 500 years.

Drink wine handed out through a window as part of an age-old tradition.

Genoa's collection of over 4 million zoological, botanical, and geological specimens from around the world.

Once home to one of the oldest banks in the world, this building is also where Marco Polo's famous travelogue was written.

This cathedral hides a sculpted dog that determines your fate and an unexploded shell from World War II.

These "anatomical machines" are only one of the many strange items in this Italian crypt.

The last moments of the ill-fated Pompeiians, frozen forever in plaster.

The middle finger of modernity.

An Italian crevasse filled with abandoned buildings gives visitors a look at the world without humans.

A cave in southern Italy adorned with thousand-year-old Biblical frescoes existed in obscurity until fairly recently.

People have been living in the cave houses on this Italian hillside since the Neolithic era.

Richard Luke Concanen never set foot on American soil.

The relics of dozens of martyrs are stored in a single chapel.

A popular legend claims that the famous pizza was invented at a restaurant in this alley.

An unusual "skull with ears" sits in the crypt of this small church tucked away at the end of a narrow alley.

The remains of the left arm of the levitating philosopher-saint are kept in a 13th-century Neapolitan basilica.

An underground paleo-Christian burial site composed of the remains of several cemeteries and Basilicas.

This shining multicolored metro station deep under Naples is said to be the most beautiful in Europe.

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

Skulls from the plague of 1656 and World War II bombings are united by a cult dedicated to caring for the ancient dead.

Secret North Korean passage discovered below the world's most dangerous border.