Opera della Metropolitana
- Presents the administrative body that protects and preserves the cathedral's artistic treasures. Includes historical notes, details on projects, services and cultural activities, as well as photographs and descriptions of the cathedral, Piccolomini librar
- http://www.operaduomo.siena.it/

About Siena
- Information about the city: history, culture, hotels, maps.
- http://www.aboutsiena.com