Built in the 4th century A.D., Santa Pudenziana is the oldest existing church in Rome.
See http://smarthistory.khanacademy.org/santa-pudenziana-rome for the source and description of the above photographs. Note in the description given there the imperial source of the halo signifying a holy Christian figure. Further, the site comments on the mosaic, noting its transformation of the Christ figure from the catacomb presentation as teacher to this post-Constantine presentation as King of Heaven. Notice, also, the imperial influences in the presentation:
The language of this passage shows the unmistakable influence of the Roman emphasis on triumph. The Cross is characterized as a trophy or victory monument. Christ is conceived of as a warrior king. The order of the heavenly realm is characterized as like the Roman army divided up into legions. Both the text and mosaic reflect the transformation in the conception of Christ. These document the merging of Christianity with Roman imperial authority.
It is this aura of imperial authority that distinguishes the Santa Pudenziana mosaic from the painting of Christ and his disciples from the Catacomb of Domitilla, Christ in the catacomb painting is simply a teacher, while in the mosaic Christ has been transformed into the ruler of heaven. Even his long flowing beard and hair construct Christ as being like Zeus or Jupiter. The mosaic makes clear that all authority comes from Christ. He delegates that authority to his flanking apostles. It is significant that in the Santa Pudenziana mosaic the figure of Christ is flanked by the figure of St. Paul on the left and the figure of St. Peter on the right. These are the principal apostles.
For videos of this church, see https://www.youtube.com/watch?v=wmVVif6_9VY ;
See https://www.youtube.com/watch?v=CchCLY_T9go; https://www.youtube.com/watch?v=TE72yuH91EY ; http://www.paradoxplace.com/Perspectives/Rome%20&%20Central%20Italy/Rome/Rome_Churches/Santa_Pudenziana/Santa_Pudenziana.htm for photographs of its exterior and interior:
See, also, https://www.google.com/search?q=Santa+Pudenziana&hl=en&pwst=1&prmd=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=g8HGToaHDMf-2QWP9vXcDw&ved=0CEcQsAQ&biw=1424&bih=775 for twenty-one pages of small pictures, without description, of its exterior, interior and art works.
See http://en.wikipedia.org/wiki/Santa_Pudenziana for some history of this basilica.
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