Not your typical flea market, the Mondscheinbazar starts at 5pm till 11pm, with musicians giving live performances while you roam around. There will even be Burlesque performances, which I have never seen live before! Drinks and food will be available as well, so the entrance fee of 3€ is decent.
It takes place in the tenth district in the ex-Anker Expedithalle, Puchsbaumgasse 1c. Directions how to get there can be found here on their website.
There is a facebook event page in case you want to read up more details.