supplication, like one would approach the Emperor. This is one of the first examples in Christian art of Christ being portrayed in the same way as the emperor or royalty. It is a concept that would later be prevalent in Christian art and architecture. In this apse Christ is not just portrayed as royalty but as the ruler of the world, of all existence. He sits atop a blue sphere, a clear symbol for the world or universe. From this perch he hands keys to Peter. This is a clear sign of Christ, and the power of heaven, giving authority and holy power to man. It is also important to note that Peter was Rome's first bishop so this meant Roman authority was sanctioned by God. This concept and picture of Christ as the almighty ruler and creator of the world would be the norm in the artwork of later churches, but it first appears here at Santa Costanza. Mosaics in the ambulatory The 4th-century mosaics on the ambulatory vault are contemporary with the building, and show a stark contrast to those in the apses, being essentially secular, with panels containing geometric patterns, small heads or figures within compartmented frames, birds with branches of foliage, vases and other objects, and vine patterns with cherubs harvesting and wine-making. This last type of scene also appears on Constantina's sarcophagus, as it does on the ends of the Sarcophagus of Junius Bassus. While the mosaics of the apses have very clear Christian imagery, those in the ambulatory are much more secular and could be considered Dionysiac with their images of grapes, fruit, birds, and mythological figures. This is especially true of the floor mosaics which were similar in style to those in the ambulatory, filled with cupids, birds, and Bacchus and grapevines. This may reflect the merging of pagan and Christian values in Rome, or alternatively construction under the non-Christian Julian. These mosaics probably represent the sort of decoration found in the Imperial palaces of the period, and in general have needed little restoration. Central dome The mosaics of the central dome no longer exist, but a picture of them can still be reconstructed as between 1538 and 1540 Francisco de Holanda made watercolour copies of what then survived. In these several biblical scenes appear, resembling catacomb paintings from the 3rd century, including Susanna and the Elders, Tobias, the sacrifice of Cain and