So named for the 21 portraits of viceroys, lieutenants and presidents of the regno Borbone di Sicilia e delle Due Sicilie, of which the first King Carlo di Borbone, crowned June 30th 1735. The portraying characters are of those who ruled Sicily, taking the place of the king who resided in Naples. Domenico Caracciolo di Villamaina and of Francesco D’Aquino di Caramanico stand out among these names. The first one in 1782 suppressed the inquisition by allocating the income of that office for the creation of the new university, and the second one, in 1788 did abolished the angherie (the work free of charge that the farmers had to do in favor of the landowner) and before France, in 1789 did abrogate personal servitude and realized in 1790 the osservatorio astronomico located on the torre Pisana of the Palazzo dei Normanni.
The value of the works in question is dictated by the possibility to extrapolate iconographic data for the study of portraits of time (from 1754 to 1840 approx.) in Sicily.
The frieze that marks the perimeter of the room in direction to the vault , was made in 1901 by Salvatore Gregorietti highlights the symbol of Sicily (Trinacria) and the eagle of the Senato Palermitano.