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

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

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

A Nesting Doll of Churches.

The final resting place of the poets Shelley and Keats.

Hidden beneath the famous St. Peter's Basilica is a veritable city of the dead that may hold the remains of St. Peter himself.

2300-year-old Roman road connecting the empire.

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

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

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

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

An alchemist's "magic door" stands in the middle of a Roman park.

The entire known universe of the ancient Etruscans is held inside this bronze model of a sheep’s liver.

This 18th-century dissection theater's frescoes display a gorgeous tension between the terrestrial and esoteric.

A dilapidated psychiatric facility on the outskirts of Milan where electroconvulsive therapy was developed and Napoleon once lived.

An ancient artistic garden parlor full of hidden water wonders.

Da Vinci's equestrian statue, 500 years in the making.

A space dedicated to contemporary art and culture, co-chaired by fashion icon Miuccia Prada.

Two very green residential towers cleaning the air in one of Europe's most polluted cities.

Long-abandoned art nouveau baths beneath Milan's Piazza Oberdan.

The odd depiction of the Virgin Mary and baby Jesus is rooted in the Catholic Church's eradication of Catharism.

The mark of the Devil's horns on a marble column in Milan.

Before there were doorbells this bronze ear was installed for visitors to announce their arrival.

This giant middle finger statue sends an unambiguous message to Italy's bankers.