The Site: The piazza before St. Peter's is a perfect ellipse; stand on one of the foci (marked red circles between each fountain and the central obelisk) and you'll see the closest set of columns line up perfectly. The Plot: Langdon races through crowds thronging the piazza to stop a murder near a Bernini carving.
The Scandal: Piazza San Pietro is baroque stagecraft at its best—and Mussolini did his best to ruin it. Bernini designed the sweeping semicircular colonnades as enormous arms to embrace (and impress) pilgrims emerging from the labyrinthine medieval alleys of the surrounding Borgo neighborhood. In 1936, Il Duce razed the Borgo to create the modern, bombastically monumental boulevard approach.