The large choir chapel, at the time of its creation, merged the environment of the Titulus with the main apse and disconnected that of the Antititulus, isolating the prothesis and the diaconicon. In fact, as is customary, the Titulo and Antititulo were present in the Sanctuary area of the ancient Norman basilica. The Antititulo, in particular, was a transverse space that divided the triapsidal area from the Titulo area. The latter also included the choir, the space for the tombs of the kings and the tombs of the bishops. The works erased the Titulo and Antititulo and also led to the creation of a transept with a dome in the centre and two chapels, one dedicated to the Blessed Sacrament and one to St Rosalie. In addition, a more incisive extension of the choir to the main apse led to the formation of a large central chapel.
