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

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

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

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.

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

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

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

A village of art and exotic creations.

A museum on the history of Paris, including a set of Napoleon's toiletries, Proust's room, and relics of the Revolution.