Historic fortifications form the boundary of Vatican City, but it’s not entirely surrounded by walls.

A treasure trove of Renaissance-era funerary art in a Roman church built on top of Nero's grave.

The Pope’s secret escape route.

Rome's first modern graffito is all that is left of a peaceful protest from the 1970s.

An 18th century fountain and two columns are all that remains of Rome's forgotten river harbor.

This basilica is dedicated to two saints, one of which is known more for his famous quote.

The martyr's wax-enhanced skeletal remains lie preserved in a glass case in the Santa Maria della Vittoria in Rome.

An enigmatic modern marker left next to a historic Roman site.

The mystic whose incorrupt corpse still attracts the faithful.

Remnants of a 4th-century church with vivid medieval frescoes and ancient sarcophagi hide beneath this old basilica.

In the early Roman Empire, people deemed traitors and criminals were tossed to their deaths from this rock.

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

This hidden alley near the location of Rome's first theater was the site of a curious miracle.

A detailed pachyderm supports Rome's smallest Egyptian obelisk.

Plaques on its facade commemorate the Tiber's most destructive deluges.

A massive marble foot is tucked away in a small alley near the Pantheon.

The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

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.

The only remaining arch of the oldest stone bridge in Rome stands in the middle of the Tiber.

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

This ancient Roman arch misled treasure hunters for centuries.

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

The best preserved Paleochristian basilica in Rome hides a number of oddities and secrets.