A rather vulgar example of the transition from Latin to the Italian vernacular.

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

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

A Nesting Doll of Churches.

Stone memorial that's said to predict the death of the pope and the site of the Cadaver Synod.

Believed to be the remains of the lost Temple of Minerva, this nymphaeum has been known by its misnomer to this day.

One of Rome's most picturesque and original bridges was also a popular choice for Grand Tour artists.

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

This large, circular tomb is the final resting place of the first emperor of Rome.

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

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

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

Ancient ruins hidden underneath a modern luxury hotel.

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

This ancient market is often referred to as the oldest shopping mall in the world.

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

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

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

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

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

A forgotten "city of water" underneath the famous Trevi district.

Inside this building is another country within Rome, a sovereign entity without a physical territory.

Breathtaking and huge 430 year old maps of Italy.

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