Just a real market in the city. If you're staying close by, go, now. Plenty of vegetable, fish, meat, deli stalls. Great place to buy anything you need, a couple of small bars with coffee, fresh beer and snacks. There is a supermarket in the basement so basically you can do all your food shopping including whatever you want to take home with you. Stocked up on Jamon and the likes in one of stalls, they happily recommended and packed in vacum bags to take home without worrying that it will go off or spread the smell in your bag.