Published in 1765, Giovanni Battista Piranesi's Osservazioni is an impassioned defense of the superiority of Roman architectural "invention" over the "beautiful and noble simplicity" of ancient Greece. In this three-part polemical masterpiece, the famed engraver and designer not only contends that the Etruscans-not the Greeks-were the artistic mentors of the Romans but also argues for a Roman-inspired exuberance in design that draws freely on all forms and traditions of ancient art. Although Piranesi's essentially Baroque vision set him at odds with the austere Neoclassicism of his...