Mona Lisa must have had the Arezzo bridge blues January 6, 2011: If you've ever wondered what the Mona Lisa is smiling about, Queen's University professor Ross Kilpatrick might have an answer. Hiding in the landscape behind her is the bridge from Petrarch's hometown of Arezzo and other clues that may indicate that Leonardo da Vinci was employing "invention"—the "technique of taking a passage from literature [...] by Harriet Staff