Unfettered by practical considerations, Giovanni Battista Piranesi created spectacular architecture realized only on paper. In his series of etched prisons, he welcomes you into the darkest recesses of his mind. Upon entering these dank, menacing dungeons, you may find yourself lost in gloomy labyrinths of stairways and catwalks littered with engines of torture and the remains of a lost civilization. Don’t worry: if the door slams behind you, it’s only your imagination.