Best known as I vespri siciliani, this expansive 13th-century epic is prime Verdi, commissioned and premiered by the Paris Opera, the company the composer called “la grande boutique.” As you will have guessed, the action is set in Sicily. Indeed, the score’s greatest hit, beloved of Golden Age bass-baritones, is “O tu Palermo,” an exile’s anthem upon coming home. As “O toi, Palerme,” it will assuredly bring down the house in this, the regal Teatro Massimo’s first French-language performances of an underexposed masterpiece. —M.G.