1. Leonardo Da Vinci, Mona Lisa, 1503–19
Painted between 1503 and 1517, Da Vinci’s alluring portrait has been dogged by two questions since the day it was made: Who’s the subject and why is she smiling? A number of theories for the former have been proffered over the years: That she’s the wife of the Florentine merchant Francesco di Bartolomeo del Giocondo (ergo, the work’s alternative title, La Gioconda); that she's Leonardo’s mother, Caterina, conjured from Leonardo's boyhood memories of her; and finally, that it's a self-portrait in drag. As for that famous smile, its enigmatic quality has driven people crazy for centuries. Whatever the reason, Mona Lisa’s look of preternatural calm comports with the idealized landscape behind her, which dissolves into the distance through Leonardo’s use of atmospheric perspective.
Photograph: Courtesy CC/Flickr/Dystopos