The most famous monument of Ravenna, being an important example of Byzantine Art and architecture was also built in the 6th century. The series of mosaics in the lunettes above the triforia, depict stories from the Old Testament. On the side walls the corners, next to the mullioned windows, have mosaics of the Four Evangelists under their symbols (angel, lion, bull and eagle). The cross-ribbed vault in the presbytery is richly ornamented with mosaic festoons of leaves, fruit and flowers, converging on a crown encircling the Lamb of God. The crown is supported by four angels, and every surface is covered with a profusion of flowers, stars, birds and animals, including many peacocks. Above the arch, on both sides, two angels hold a disc and beside them a representation of the cities of Jerusalem and Bethlehem. They symbolize the human race -  Jerusalem representing the Jews, and Bethlehem the Gentiles. [Wikipedia]