The triumphal arch mosaic of Santi Cosma e Damiano, Rome. It originally dates from the 6th century, but may have been completed in the time of Pope Sergius I (692-701). Its symbolic images are based on chapters 4 and 5 of Revelation and cover two windows of the 4th-century Roman hall. In the center, the Lamb of God lies on a jewelled throne, beneath a cross and above a scroll with seven seals. The Lamb is flanked by seven jewelled candlesticks (representing the seven spirits of God) and four angels. On the left is the winged man symbolising Matthew and on the right is the eagle of John the Evangelist. On the bottom sides of the arch are the arms of some of the 24 Elders carrying crowns; the full-length figures and other two evangelists were lost during the 17th-century renovation.