 Structure, however, maintained the orthogonality of the monumental complex of the Jesuit College and by a dense corollary of patrician houses and numerous churches (over 20).In an elevated position and strategically dominant stands the Castle, erected or at least altered by Frederick II in the thirteenth century, on the basis of an ancient Greco-Roman fortress later used by the Arabs and Normans, trapezoidal with three towers and two square and a circular plan.On the site where stood the ancient medieval mother church, dedicated to Our Lady of the Angels and probably built over a mosque and a temple of Venus, in 1615 began the construction of the Cathedral, designed by the architect Mariano Palermo Smiriglio and completed in 1761, at least with regard to the longitudinal body, as from this date their work began to expand the old apse.