Geometry in Islamic Architecture
http://www.sakkal.com/islamic_geometry/rib_domes.html

Muqarnas : A Three-Dimentional Decoration of Islam Architecture
http://www.tamabi.ac.jp/idd/shiro/muqarnas/map.html

Alto medioevo
http://it.wikipedia.org/wiki/Alto_Medioevo
http://www.iisalessandrini.it/progetti/medioevo/am.htm