The engineering wonder and pleasure dome of a much-maligned emperor still holds undiscovered secrets.

The astonishing collection of an infamous criminologist.

Jesus' footprints and the first catacombs in the world.

This quaint Italian town keeps losing ground as the sides of its plateau slowly erode.

David Sedaris called it "The greatest shop in the world."

A fairy tale castle in modern Rome.

Venice's island of the dead.

The plague quarantine island home to the alleged "Vampire of Venice."

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

Hidden beneath the famous St. Peter's Basilica is a veritable city of the dead that may hold the remains of St. Peter himself.

Ever hear of the Milazzo Cage?

Medieval town turned hippie commune, once home to the secret foreskin of Jesus Christ.

The final resting place of the poets Shelley and Keats.

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

Architectural monsters are devouring this palace's every door and window.

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

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

2300-year-old Roman road connecting the empire.

The yawning maw of this pagan visage is said to bite off the hands of liars.

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

The once forbidden "secret cabinet" of erotic art from excavations of Pompeii and Herculaneum.

An Italian hillside ghost town.

A large grotto built in the 16th century amidst Florence's famous Boboli gardens.

Sitting on an Italian hilltop is this surreal fortress built by the mad inventor of electrohomeopathy.