For drop-dead operatic dazzle on the colossal scale, the Bregenz Festival’s floating stage at the Austrian end of Lake Constance takes a back seat to no showcase on earth, not even Verona’s fabled arena. Conventional scenic design is useless here. The action is far away. Nuance is a lost cause. What’s needed is an extravagant visual metaphor that distills the essence of the classic at hand. Engineered like spaceships, each show takes months to build and runs, to almost invariably sold-out houses, for two seasons. The new attraction this year is Rigoletto, Verdi’s twisty tragedy of a court jester’s revenge. —M.G.