In the external side of the left transept, just below the edge of the roof, a palindrome magical formula is inscribed in a stone plaque. This Latin sentence, that reads “SATOR AREPO TENET OPERA ROTAS”, is an example of Sator Square and it lays out on three lines that may be read left-to-right or right-to-left. The architrave of the left-side portal features a stone carving which represents a wild boar hunting scene referring to Etruscan and Roman tradition.