The long, fast-moving line of businesspeople and tourists tips you off to the fact that this cafeteria-style spot just off the Freedom Trail is a bargain. The food is good, too. You can fill up on a couple of slices of pizza, but if you're feeling adventurous, try arancini (a rice ball filled with ground beef, peas, and cheese). Calzones -- ham and cheese, spinach, spinach and cheese, or spinach and sausage -- and potato croquettes are also tasty. Study the cases while you wait and be ready to order at once when you reach the head of the line. Have a quick lunch and get on with your sightseeing.