Wikipedia: Duomo di Milano
- An illustrated history and description of the second largest Gothic cathedral in the world from the collaborative encyclopedia.
- http://en.wikipedia.org/wiki/Duomo_di_Milano

Florence Cathedral
- The official site provides an illustrated history and bibliography of the famed Santa Maria del Fiore, with its octagonal baptistry and Renaissance cupola. Includes plans of mosaics and frescos.
- http://www.duomofirenze.it/

Cathedral, Pisa, Italy
- Images, commentary and bibliography from Great Buildings Online.
- http://www.greatbuildings.com/buildings/Cathedral_of_Pisa.html

Cathedral of S. Maria Assunta, Orte, Italy
- Photograph and brief history from Christus Rex.
- http://www.christusrex.org/www2/comuni/orte/catten.htm

St. Peter's in Rome, Italy
- Images, commentary and bibliography on this great cathedral from Great Building Online.
- http://www.greatbuildings.com/buildings/St_Peters_of_Rome.html

The Duomo, Siena
- A beautiful example of the convergence of Gothic and Romanesque - squat, round domes and arches offset by soaring towers. Expandable photographs and description from Digital Imaging Project.
- http://www.bluffton.edu/~sullivanm/sienacath/duomo.html

Passing Through St. Peter's
- A gallery of beautiful images of the central cathedral of the Catholic faith provided by Eternal Word Television Network.
- http://www.ewtn.com/gallery/sp/sp1.htm

Orvieto Cathedral, Italy
- Photographs, commentary and bibliography on the Gothic cathedral designed by master mason Arnolfo di Cambio and built 1290 to 1500, provided by Great Buildings Online.
- http://www.greatbuildings.com/buildings/Orvieto_Cathedral.html

The Leaning Tower of Pisa
- The official site gives an illustrated history of the famously tilted medieval cathedral bell tower, Quick Time Virtual Reality panoramas and huge searchable archives of photographs and historical sources.
- http://torre.duomo.pisa.it/index_eng.html

Pisa in Virtual Reality
- ComPart provides interactive 360-degree QuickTime panoramas of the superb architectural ensemble of Cathedral Square, the cloistered churchyard, Baptistry and Cathedral, with brief descriptions.
- http://ww2.webcomp.com/virtuale/us/pisa/movie.htm