This mosaic by Pietro Cavallini (1240–1330) is situated in the apse of the Basilica di Santa Maria in Trastevere, Rome. It shows Mary as the mother of God, sitting next to Christ. In this type of Byzantine iconography, Mary is presented as "basilissa" (Greek: βασίλισσα), i.e. as queen or empress of the world, sharing the throne of her son. The Basilica di Santa Maria in Trastevere is one of the oldest churches in Rome dedicated to Mary. The mosaics by Pietro Cavallini date back to the 1290s.
Basilica di Santa Maria in Trastevere, Rome, colour photograph, 2016, photographer: Fczarnowski; source: Wikimedia Commons, Attribution-ShareAlike 4.0 International (CC BY-SA 4.0).