Karmelitermarkt has catapulted itself from forgotten grocery stall compound to trendy neighbourhood market in recent years. The market is quieter and smaller than Naschmarkt, but has lovely eateries such as Marktachterl and Viennese/Georgian fusion tavern Madiani.
The market is located in Leopoldstadt just across city centre and Danube Canal, an up and coming area for young families and urban professionals. The former Jewish quarter still boasts a good amount of Jewish neighbourhood, which provides part of the market's character.
My tip: Visit for a Saturday brunch, probably on your way to Augarten park and porcelain museum (10 min walk).