The three halls create an open courtyard, in which was originally located a separate baptistery. Surviving from both large basilican halls are rich mosaic pavements showing (amongst other scenes) Jonah and the Whale, and a series of, mainly female, donor portraits. It appears that similar cathedrals of double-basilica and baptistry were soon afterwards erected in Milan, Trier and Pavia; but that subsequently single-basilican churches became the more common cathedral model.