Arthur,
I hope you read this- you should not miss the 'Gelato di San Crispino' at Fontana di Trevi- facing the fountain take the road on your right (t's the second road clockwise facing the fountain) and then take the second road on the left. It's a small gelateria shop it may be better to ask the locals as they can tell you exactly where it is. Buona vacanza!
