Osteria ai Mercati may be newer than other restaurants in the Testaccio area, but it feels like an old fit. Start with simple bruschetta with different toppings: fresh, sweet tomato, or smoked salmon and arugula. Potato-stuffed ravioli and ciecamariti (literally "blind the husbands," pasta in a spicy tomato sauce) are excellent, and second courses such as pork with porcini mushrooms and chestnuts are well executed. Homemade desserts and liqueur top off the meal.