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

A large replica of a monumental Roman inscription is located on the side of this museum.

This ancient Roman arch misled treasure hunters for centuries.

A 15th-century monumental Latin inscription on this house celebrates Lorenzo Manilio's love for Rome.

This medieval church in Rome was almost destroyed following a terrorist attack in 1993.

An ancient Egyptian obelisk is now used to commemorate fallen Italian soldiers.

An 18th-century post box used to alert the church of sick and ailing foreign pilgrims.

An unremarkable wooden wheel built into the side of one of Rome's oldest hospitals was part of a policy to reduce infant exposure.

This small church was constructed over the ruins of three temples dating to the Roman Republic.

Plaques on its facade commemorate the Tiber's most destructive deluges.

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

A Nesting Doll of Churches.

Ancient ruins hidden underneath a modern luxury hotel.

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

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

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

Architectureal fantasy quarter of Rome.

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

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

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

These spartan apartments are provided to clergymen visiting Vatican City.

This series of Baroque passageways in Vienna's cultural center mix old architecture with modern art.

A neo-Gothic church built to thank God for saving the Emperor of Austria from an assassination.

The beautiful baroque library of the Hapsburg empire.