The triumphal arch mosaics of Santa Maria Maggiore in Rome have long posed a puzzle for scholars. In addition to the events surrounding the birth of Jesus and his subsequent designation as the Messiah sent from Heaven, there are also contemporary messages that have particularly engaged iconographic research for a long time. Within the late antique visual program, some figures appear that are not mentioned in the biblical tradition and make references to the apocryphal infancy gospels and the sermons of Leo the Great. Additionally, some scenes contain subtle allusions to the imperial ruler iconography of the Eternal City, suggesting that the late antique idea of Rome is evidently manifested here. All previous studies on the topic present somewhat contradictory viewpoints, and the possible interpretations also show differences.