This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
If Greece and Rome established mosaic as a technique, the Byzantine Empire transformed it into a theological instrument. Where Roman mosaicists had used stone tesserae mainly for floors and reserved glass for occasional wall decoration, Byzantine craftsmen reversed the emphasis entirely, covering the walls, vaults and domes of churches with glass tesserae set against gold, so that entire interiors glittered with reflected light. In Byzantine work, solid fields of gold tesserae came to form the background of nearly every major decorative scheme, a shift with no real precedent in the more measured, earth-toned palettes of earlier Greek and Roman floor mosaics. The Church of San Vitale in Ravenna is a defining example of this new purpose. There, mosaic figures were rendered as ethereal and weightless, floating against gold grounds that dissolved any sense of real architectural space behind them, an effect meant to place the worshiper in the presence of a heavenly rather than an earthly realm. Byzantine art moved away from the naturalistic modeling that Greek and Roman artists had pursued, toward flattened, frontal figures with angular forms and sharp contours, a style seen most clearly in its mosaics and icons and one that went on to shape Italian painting for centuries afterward. This was also a shift in what mosaic was understood to be for. Ancient pebble and tessera floors, however skilled, were largely decorative, laid where feet would walk over them. Byzantine wall and vault mosaics were instead devotional, placed exactly where the eye and the light would meet, executed by craftsmen whose technical advances let mosaic develop into a genuinely powerful form of personal and religious expression rather than simply architectural ornament. That religious, monumental use of mosaic proved durable well past the empire's own borders and centuries. Long after Rome and Byzantium, the same gold-ground tessera vocabulary would resurface far from any church, in Antoni Gaudi's broken-tile facades in Barcelona and in Boris Anrep's mosaic floor for Tate Britain, evidence of how far the Byzantine reinvention of the medium ultimately traveled.