The "Great Sewer" of ancient Rome is one of the oldest sewer systems in the world, and is still in use.

Inside this McDonald's you can dine on your Big Mac and fries next to a 2,500-year-old Roman wall.

This hill made entirely of ancient Roman jars was simply a garbage dump to the people of the time.

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

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

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

Installed in an act of one-upsmanship, the annual sundial in this church is also a symbolic victory for the Gregorian calendar.

More sculpture than building, this architecturally significant temple was built on the spot of Saint Peter's crucifixion.

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.

This beautiful park on the outskirts of Rome protects the ruins of two colossal ancient aqueducts.

Jesus' footprints and the first catacombs in the world.

The final resting place of the poets Shelley and Keats.

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

2300-year-old Roman road connecting the empire.

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

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

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.

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."

Museum preserving torture methods from the past.

This surreal statue brings a famous French novel about a supernatural cad to arresting life.

Medieval museum built over Roman baths that features famous tapestries of a lady and a unicorn.