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

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

The oldest public library in Ireland.

Buried for centuries, this hidden cellar is all that remains of London's medieval Whitefriars Monastery.

This amazingly well-preserved villa just outside Pompeii boasts rare examples of ancient Roman paintings.

A huge enchanting public park just outside the ancient walls of Rome.

This Roman arch marks the location of an ancient gate at one of the Seven Hills of Rome.

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

This immaculate and historic water garden culminates in a massive stone dining table with an inset fountain for chilling the wine of the Cardinal's guests.

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

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

Ruins of a 10th century church tucked away deep in a botanical garden.

A fairy tale castle in modern Rome.

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

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

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

2300-year-old Roman road connecting the empire.

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

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

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

Architectureal fantasy quarter of Rome.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

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

A 16th-century horror show built in a lovely Italian garden.