Detail of mosaic on the left wall of the apse (c.547 AD) depicting Emperor Justinian (r. 527-65) and his entourage. Justinian was one of the most powerful Byzantine emperors and a great church-builder. He stands in the center of the mosaic, wearing imperial purple and holding a large gold paten, the plate on which the bread is placed for Mass. To his left is Maximian, Archbishop of Ravenna, holding a jeweled cross. Some of the other men hold objects as well, including a censer, an ornate book, and a soldier's shield displaying Christ's monogram, the Chi-Rho.