2 links
Early Christian and Byzantine Art and Architecture
campus.belmont.edu
Belmont University offers pages of annotated, expandable thumbnail images of Christian structures and art ranging from the Catacombs of Ancient Rome to the 12th century.
Margaret Visser: The Geometry of Love
margaretvisser.com
A book exploring the basilican church of Sant Agnese fuori le Mura, Rome, rebuilt 625-38 to replace a 4th-century church. Author's biography, reviews, images with extracts.