The astonishing collection of an infamous criminologist.

This abandoned Brutalist treehouse is a hidden architectural relic.

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

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.

A Milanese café entirely designed by the American director Wes Anderson.

One of several skulls claiming to belong to the beheaded St. John the Baptist is on display at this Roman church.

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

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

This giant middle finger statue sends an unambiguous message to Italy's bankers.

A labyrinth of ancient tunnels hidden below the city holds the ruins of 2,500 years of history.

The skull of the patron saint of lovers lies in the Basilica di Santa Maria in Cosmedin—maybe.

The underground sanctuary of a mysterious ancient cult.