Vienna has a lot of markets. Basically each neighborhood has its own. But none is more visited and famous among tourists than the Nachmarkt. The location and the prominence make the market the most multicultural, expensive and perhaps overvalued. Maybe this is also the last place that a Viennese will recommend. Yet because of it's beautiful and central location it is still a nice sight to visit. Especially on Saturdays!
Every single Saturday the Nachmarkt stretches out and overrated delicacies make way for vintage, antiques and other unique, ancient objects. For those who love old stuff, this Viennese flea market is a must.
You can find here old books, traditional austrian garb, silverware, tableware. Probably something you have been looking for and most definitely a lot of stuff you don't need.
Getting there: take the green subway line U4 and get off at Kettenbrückengasse station. The market is in between the Rechte and Linke Wienzeile streets.
If you loose focus on the goods, you'll notice how gourgeous the street of the market actually is. And as I mentioned above, the location is very central and hence many other sites are close. Karlskirche and the Opera are two spectacular buildings you probably won't miss when you'll check out the Naschmarkt. But if you're into art than don't forget to take a look at Seccesion (contemporary art & Klimt) and Academie of Fine Arts (Bosch).