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

Hidden in an Italian forest is a completely homemade amusement park that has taken a lifetime to create.

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

The glowing blue Nymphaeum of Emperor Tiberius.

Venice's "Island of the Mad."

The final resting place of the poets Shelley and Keats.

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

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

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

2300-year-old Roman road connecting the empire.

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

Thousands of well-dressed mummies below a monastery.

According to the local folklore, the myriad colors of this lake are the result of a lovelorn wizard's blunder.

The only "Egyptian" pyramid in Europe and the legendary tomb of Remus.

Stalactites and stalagmites in a beautifully lit cave.

Pompeii's less famous neighbor is still revealing her secrets.

The underground sanctuary of a mysterious ancient cult.

The middle finger of modernity.

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

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

Rome's semi-secret peephole vista is also a former Crusader stronghold.

This hidden Art Nouveau courtyard is an opulent feast for the eyes.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

An alchemist's "magic door" stands in the middle of a Roman park.