In the east intrados of the chapel are medallions with busts of Christ,
at the centre, and of six apostles, including Peter and Paul, identified
with inscriptions bearing their names. Saint Paul is depicted according
to his traditional features, with a receding hairline touched by a small
tuft of hair, a long dark beard, large thoughtful eyes – instruments
of divine contemplation. The mosaic is realised almost like a highly
refined painting, through lines that define the volumes of the face
thanks to the juxtaposition of tesserae in delicate hues. Blue-grey,
light blue and white tesserae define the volumes of the tunic, while
the more illuminated folds of the cloak is rendered in brown and ochre
tesserae. The portrait of the apostle-philosopher emerges from an
indigo background, and is surrounded by an aura of lighter tesserae.