• The original apse of Pope Sixtus III (432-440) was replaced by Pope Nicholas IV (1288-1292). Pope Nicholas IV was a Franciscan and so he commissioned the Franciscan friar Torriti for the work. Thus also St. Francis of Assisi and St. Anthony of Padua appear in the mosaic. Torriti had recently completed the apse mosaic at St. John Lateran. Pope Nicholas IV is buried near the entrance of the church

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• Most of the scenes relate to events in the life of Mary as this is the church of S. Maria Maggiore

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• At the top center of the inner arch, representing Jesus, is a lamb on a throne. This is connected with the mosaic on the sides of the inner arch