According to the historical record: “In 1185, Archbishop
had images of saints painted on the ceilings, beams and their modillions against a gold background, either in their entirety or up to their navels. Several images of saints have been painted here which, because of their height, escape the eye so much that they cannot be identified by those standing on the floor of this temple. Full names marked in Greek letters are added to the pictures.”
The interior walls were not decorated, but finished in “ pietra rasa ” with a light coating of plaster, which gave the interior of the cathedral a soft glow that brought out the dominant yellow-gold and blue colours of the roof.
No preparatory traces of a mosaic covering have been found, whereas the mosaic covering is characteristic of the contemporary construction of the Monreale Cathedral .
The floor was made up of “marble tiles and precious stones, i.e. mosaic flecked with various coloured incrustations, with different slabs cut at once and diversified in various kinds”.
Therefore, it was a “ cosmatesque ” mosaic floor, a decoration typical of the medieval period and characteristic of the floors of other contemporary Norman churches, with the exception of the Cefalù Cathedral which has a red mamo floor in the presbytery area and grey lumachella limestone in the naves. In later centuries, the largely degraded mosaic floor was replaced with large marble and granite slabs, interspersed with tomb slabs, for the custom of burying the bodies of prelates and nobles inside churches.
This particular feature, now lost, gave Palermo Cathedral the distinction of being counted by historians as one of the churches with the greatest number of tomb slabs inserted within its flooring.