This mosaic of Christ is in the apse of a small Byzantine church in Thessaloniki, Greece which is called Hosios David. The mosaics date from the 5th or 6th century, making them very rare examples of pre-iconoclastic art. In the 8th through the 9th centuries the Byzantine Empire went through phases of iconoclastic rule. Thousands of representations in various media were destroyed by the Byzantines as those who thought god was angered by icon worship (idolatry) attempted to purge the Empire of its images. Thus few works of art from before this period survive. These mosaics at Hosios David were just covered up rather than destroyed, saving them for us to see today. Note that the image of Christ hasn’t yet become the bearded, long-haired hippie we usually associate with him; he’s a young, beardless shepherd, which is how he was commonly depicted in Christianity’s early centuries. The image looks a bit distorted because it’s in the semi-dome or apse of the church. Christ is surrounded by the symbols of the Evangelists: the lion for Mark, the winged man for Matthew, the eagle for John, and the ox for Luke.