Christian mosaic art also flourished in Rome, gradually declining as conditions became more difficult in the Early Middle Ages. 5th century mosaics can be found over the triumphal arch and in the nave of the basilica of Santa Maria Maggiore. The 27 surviving panels of the nave are the most important mosaic cycle in Rome of this period. Two other important 5th century mosaics are lost but we know them from 17th-century drawings. In the apse mosaic of Sant'Agata dei Goti (462–472, destroyed in 1589) Christ was seated on a globe with the twelve Apostles flanking him, six on either side. At Sant'Andrea in Catabarbara (468–483, destroyed in 1686) Christ appeared in the center, flanked on either side by three Apostles. Four streams flowed from the little mountain supporting Christ. The original 5th-century apse mosaic of the Santa Sabina was replaced by a very similar fresco by Taddeo Zuccari in 1559. The composition probably remained unchanged: Christ flanked by male and female saints, seated on a hill while lambs drinking from a stream at its feet. All three mosaics had a similar iconography.
Is there an answer to this question (If it cannot be answered, say "unanswerable"): What was similar between the three most important 5th century mosaics?
iconography