The theme presented through the mosaics is the victory of eternal life over death, attainable through God.
Look for example at the mosaic above the entrance: there God is depicted in the guise of the Good Shepherd, sitting in the midst of his flock, the faithful. It means that only through God is eternal life attained. Notice how all six sheep confidently turn their eyes right toward the shepherd, one even approaching to be petted.
Look around, admire the richness of colors and details, from the main subjects to the simple decorations, garlands, flowers and colorful Greek patterns. Have you noticed the presence of some animals such as doves, deer, and fish?
They were not only included for decorative purposes; in fact, they have symbolic value for the Christian religion.
The deer recalls an Old Testament passage that says: "as the doe yearns for streams of water, so my soul yearns for you, O God."
And indeed, you may have also noticed the repetition of water-related images such as fountains or springs. These also have significance: they represent the source of eternal salvation, that is, God, by whom souls can quench their thirst.
All this beauty was supposed to guard the eternal sleep of Galla Placidia and other members of the imperial family, but it is not known who was buried in the three stone sarcophagi you see protected by niches. The central one, which seems unfinished, is thought to have contained Galla Placidia.
The sarcophagus placed further to the left was probably arranged to hold the remains of Constantius III, Galla's husband, while the one on the right was intended for her son Valentinian III.
An interesting fact: It is most likely that Galla Placidia's body was buried in the Chapel of Santa Petronilla in Rome, where a beautiful sarcophagus was found in the 15th century that contained the remains of an adult and a child, perhaps the noblewoman herself and her first child, Theodosius, who died shortly after birth.
