Divino Rosso is a narrow wine bar on Piazza della Repubblica, almost facing the cathedral, with a few tables outside and a long bar inside lined with bottles. The owner is happy to walk you through the difference between Fine, Superiore, and Vergine Marsalas, and will put together a flight of three or four for not very much money.
There is a small kitchen for cheese and salumi plates and a short selection of pasta. It is open late and gets busy after dinner.