A mysterious chasm in the heart of the ancient Roman Forum, the Lacus Curtius was once believed to be a gateway to hell.

This ancient Roman prison is decorated with an upside-down cross not as blasphemy but as saintly tribute.

A Nesting Doll of Churches.

This ritzy Italian market is built around a statue of an unforgiven heretic who was burned for his belief in an endless universe.

Jesus' footprints and the first catacombs in the world.

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

The underground sanctuary of a mysterious ancient cult.

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

2300-year-old Roman road connecting the empire.

Rome’s legendary peephole vista is also a former Crusader stronghold.

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

In Florence's great Duomo, a 26 foot fresco honors a mercenary famous for attacking Florence.

A copy of the famous statue can be found in this Florence piazza, along with one of the most breathtaking views of the city below.

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

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

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

The naturally mummified body of a peasant girl saint.

Fortified medieval tower house with lovely roof garden.

This bustling Italian plaza is built on the ruins of an ancient Roman amphitheater.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

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

This enormous, elaborate tomb looks oddly out of place next to a suburban Edinburgh bowling club.