Please answer a question about the following article about Mosaic:

Important fragments survived from the mosaic floor of the Great Palace of Constantinople which was commissioned during Justinian's reign. The figures, animals, plants all are entirely classical but they are scattered before a plain background. The portrait of a moustached man, probably a Gothic chieftain, is considered the most important surviving mosaic of the Justinianian age. The so-called small sekreton of the palace was built during Justin II's reign around 565–577. Some fragments survive from the mosaics of this vaulted room. The vine scroll motifs are very similar to those in the Santa Constanza and they still closely follow the Classical tradition. There are remains of floral decoration in the Church of the Acheiropoietos in Thessaloniki (5th–6th centuries).

What is considered the most important surviving mosaic of the Justinian age?
The portrait of a moustached man