Knowledge for the conservation: the case of the Quattro Canti Square in Palermo (Sicily)

Located at the intersection of Corso Vittorio Emanuele and Via Maqueda, the "Quattro Canti" (Four Corners) is the crossroad marking the heart of Palermo's old historic district. The project for the layout of the square was drawn up in 1608 from the Viceroy Duke of Maqueda. It is also referred to as the "Theatre of the Sun", since it is illuminated by the sun's rays from dawn to dusk. Fountains, statues, columns and coats of arms adorn the curved facades of the palazzos that stand at each corner in a splendid symmetry. Each corner has three tiers of decoration - at ground level there are fountains representing the four seasons. Above the fountains stand statues of the four Spanish kings (Charles V, Philip II, Philip III, and Philip IV), and above them stand four saints - Santa Ninfa, Santa Cristina, Sant’Oliva, and Sant’Agata - all of whom were reputedly born in Palermo. Stones used for the building are calcarenite, Carrara marble and Billiemi stone. The four prospects have been subjected to restoration works carried out in 2000-2001 by the local Superintendence, after extensive diagnostic studies. After 14 years from the intervention, the surfaces show inevitably processes of alteration related to the high vehicular traffic afflicting the road junction. The study focuses the characterization of the state of conservation of the stone surfaces that leads to some considerations on the evolution of the degradation. Moreover, starting from the existing documentation, by making an effective diagnostic plan is it possible to contribute to a better control and management of the cultural heritage