Oh, tourists. At Rome's Trevi Fountain, inappropriate tourist behavior is forcing the government to change some rules. Here's what to know.

For many a first-time traveler to Rome, a stop at the Trevi Fountain is a must—though not so much to gaze at it. As the superstition goes, if you face away from it and toss a coin with your right hand ...

At the fountain, the collected coins are weighed under the oversight of city police officers before Marchioni takes them to ...