Just because it's noon and you only have time between sights for a sandwich doesn't mean that it can't be a satisfying, even awe-inspiring one. There's no menu at All'Arco, but a scan of what's behind the glass counter is all you need. Order what entices you, or have Roberto or Matteo (father and son) suggest a cichetto or panino. Options here are broad enough to satisfy both conservative and adventurous eaters. Wine choices are well suited to the food. Arrive early or at the tail end of lunchtime to snag one of the few tables in the calle.