A couple enjoys the last evening of the season at the Bar Cutroni Michele, one of the numerous outdoor cafés that spring to life each summer and vanish each fall along Turin’s Lungo Po Murazzi—the sidewalk beside the Po. Yet few are fooled by the river’s summer calm, which is often followed by autumn floods. The torrents of November 1951—the modern benchmark—inundated more than 450 square miles, displaced some 200,000 people, and left an indelible mark on the consciousness of Italy.