Although sitting at an outdoor table in a cafe on the square is costly, the Tre Scalini on Piazza Navona is the place to eat the famous Tartufo dessert, a rich handmade chocolate ice cream roll. It's worth the splurge if you take your time eating and enjoy taking in the scene. So just think of it as the price for some great outdoor entertainment. You can also get the tartufo to go if you prefer, for half the price.