A burial vault located under Tiber Island in the middle of the Italian capital.

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

This gallery commissioned by Cardinal Spada is known for its magnificent optical illusion.

In Rome’s Jewish ghetto, a 200-year-old bakery still makes the neighborhood’s historic sweets.

Rome's semi-secret peephole vista is also a former Crusader stronghold.

This hidden Art Nouveau courtyard is an opulent feast for the eyes.

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

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

A Nesting Doll of Churches.

An abandoned Roman salami factory has found new life as an art space home to 200 squatters.

The Pope’s secret escape route.

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

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

The skull of the patron saint of lovers lies in the Basilica di Santa Maria in Cosmedin—maybe.

The underground sanctuary of a mysterious ancient cult.

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

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

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

A 6,888-carat piece of turquoise that bears a striking resemblance to the first President of the United States.

Although damaged beyond recognition, this stone god is still said to bring good luck to those who tap on him with a pebble.

This bizarre residential building is the masterpiece of Von Jour Caux, the “Gaudí of Japan.”

Designed by a computer, this intricate network of fluorescent green pipes has taken over a subway station.

These unique toilets feature transparent glass covered in PDLC film.

Kawaii meets poisonous at this unique art gallery.