See also Art by Time Period: Archaeology and Ancient World.
Art by Time Period: Renaissance and Baroque
Art by Time Period: Medieval
Acque Urbis Romanae: The Waters of the City of Rome. Cartographic history of water systems in Rome.
Getty Museum Open Content Program. High resolution images of works from the Getty that are in the public domain and may be used FREELY. Recent additions include Max Hutzel Photographs of Art and Architecture in Italy and 15th through 18th century tapestries.
Paradoxplace: An amateur site with many photos of Italian architecture. Images may be used for educational purposes with proper attribution.