One thing I don't like about thrifting? Dusty hands after. I love old things but the fact that you have to dig through loads of moldy, dusty things kills me. The more impressed I was when I found the Mulholland Drive Vintage Shop in Krakow. It's the most well kept and fanciest second hand store I've ever been to. Unfortunately one of the blouses I bought had a little rip on the arm, which I realized after buying it. But other than that I was super impressed by everything and really loved the cute girl by the cash desk.
Another secret spot, a little less posh, is Plac Nowy in the Kazimierz district. It's a little square with venders that sell jewelry, old bags, clothing but also food and flowers. You can find the most amazing leather goods there!