If you've seen La Dolce Vita by Fellini you'll recognize this spot easily. The fountain lies in a small piazza off Via del Tritone. It was designed by Nicola Silva. Legend goes that by throwing a coin in the fountain you can secure your return to Rome (we didn't do it, but I still have hopes to return). We went there in the afternoon; we were not looking for the fountain, just wandering the streets and ended up here. It was extremely crowded, almost imposible to get near the fountain. I don't know which hour is better, my guess is that it is crowded all the time. Maybe early morning will be a better time if you wish to avoid the crowds. (from: http://andreea.francu.com/travel/rome.vr/places.vr/).