You can easily divide the whole Roman population into factions that hate each other if you ask them which gelato shop makes the best pistachio ice cream. Because pistachio is easily the most important ice cream flavor of them all. If pistachio is good, you can probably be sure all the other ones are good. Don’t ask me why, it’s the rule.
Gelateria dei Gracchi makes the best pistachio there is and I am ready to fight anybody who will say otherwise. And even if you don’t like pistachio (you’re a disgrace) all their fruit-based flavors are among the top of the top of Roman ice cream and clear of any lactose, so that is definitely something to appreciate. My second favorite flavor is apples and cinnamon. But still, pistachio is a major key.
In addition to the main shop, there is a new one right next to Piazza del Popolo in via di Ripetta which is just as good. It is also very appreciated they are very clear about allergens and similar and pay extra attention to that-not-so-small detail. I wish more gelato shops in Rome would do the same thing.