The Antititulus, in the Palermo Cathedral, is a longitudinal room, with an almost transept-like appearance, arranged in front of the three apses. Next to the Titulus and Antititulus are the sacristies, which have now been converted into the Cathedral Treasury. The Titulus, on the other hand, is the space where the Canons Regular sat, taking their place in the choir, and which contained both the bishop’s chair and the royal seat.