Detail of St. Paul in the Procession of the Apostles mosaic at the Baptistry of the Arians, Ravenna, Italy. The Baptistry was erected by Ostrogothic King Theodoric the Great between the end of the 5th century and the beginning of the 6th century. When this mosaic was made, Ravenna was the capital of the Western Roman Empire and the center of late Roman mosaic art.