A fortified medieval basilica on the Caelian Hill preserves extraordinary frescoes and one of Rome's most beautiful hidden cloisters.

Once strictly off-limits, this lower level housing curious and priceless vehicles of the Petersen Automotive Museum is now open to the public.

Where the line between entertainment and aerospace blurs.

Its interior is adorned with some of the best examples of early Christian mosaics.

A small cell adjacent to this church was once the bedroom for a renowned saint.

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

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

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

Known for centuries as the famous Roman emperor's burial place, this monument is actually something else.

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

A colossal aqueduct from the second century B.C., deeply hidden in a gorge on the outskirts of Rome.

Roman politician Herodes Atticus built this nymphaeum to honor his wife, whom he may have murdered.

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

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

This small, ancient Roman temple was once a church dedicated to the patron saint of penitents.

The remains of this 2nd-century Roman temple are incorporated into a modern building.

These hut foundations are believed to be the residence of Romulus, founder of Rome.

An ancient Roman temple first dedicated to an emperor's wife is now a church.

A monumental fountain in Rome features a large statue of Moses that has been criticized for centuries.

According to local folklore, this Roman sepulcher was once a throne for the Devil.

This small Roman arch was transformed into a dwelling by the founder of the Trinitarian Order.

A rare example of a medieval house in Rome adorned with a melancholic inscription.

Hollywood's most famous landmark, the "temporary" sign that has stood for decades longer than intended.

Fake subway tiles were installed to cover a design that resembled the Confederate flag—it's unclear if the resemblance was intentional.