Fontana di Trevi
A shot of the crowds in the Piazza di Trevi.
If the pickpockets don't relieve you of it first, throw a coin into the Trevi Fountain and legend has it that you'll some day return to Rome. Virtually every visitor tosses a coin (I did) which adds up to a pretty penny in the pool seen in the foreground.
The cache belongs to the Catholic charity Caritas, but there was uproar in 2002 when newspapers reported that a homeless, officially unstable man by the name of Roberto Cercelletta had been conducting dawn raids of the fountain for more than 30 years and netting up to €500 a day. He used to have a lie-in on Mondays, allowing the Caritas team to wade in.