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

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

The Pope’s secret escape route.

One of several skulls claiming to belong to the beheaded St. John the Baptist is on display at this Roman church.

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

This beautiful park on the outskirts of Rome protects the ruins of two colossal ancient aqueducts.

A fairy tale castle in modern Rome.

Jesus' footprints and the first catacombs in the world.

The final resting place of the poets Shelley and Keats.

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

2300-year-old Roman road connecting the empire.

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

The underground sanctuary of a mysterious ancient cult.

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.

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

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

Architectureal fantasy quarter of Rome.

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

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

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

Memorial to the lost dead of Gdansk, whose resting places were destroyed during World War II.

This 700-year-old structure is one of the most unique architectural and historic monuments in Gdańsk.

The site of the first battle of World War II.