What can one do in Palermo on a Sunday? The markets are all closed and the sites seem to close early in the day.
Museums are open in the morning. Go up to Monreale to see the magnificent cathedral and its breathtaking mosaics. Take a bus to Mondello, have a fantastic seafood pranzo (lunch) and take a dip. Or have a long lazy lunch in town and wander through the pedestrian streets and do some window shopping and people watching, like the Palermitani do. Have pane panelle at the Antica Focacceria San Francesco. If you're into ghoulish stuff, go to the catacombs. Eat pastries and gelato. Have a drink on the pedestrian main drag, Via Maqueda. In other words, make like a Sicilian in a fascinating multilayered city on a Sunday.