There are so many markets and stores that it is well worth a day trip. You can walk around all day and visit the markets and shops. There aren’t many quality products to buy, but it is neat to see and get a feel for the area. We spent the morning walking around, had a long lunch, and then did a second walk, a self-guided tour onto many side streets. It was all very interesting to see.
Watch out for the scooters, but otherwise, you should be safe. There are lots of police around as well. If you can, try to go in on a day that the cruise ships aren't there, as you will have more opportunity to walk freely. There is a mall to visit, as well as many types of stores and eateries.