Even if you’re not interested in a hand-crocheted Nepalese hat, a set of turn-of-the-century doorknobs, or any one of thousands of second-hand trinkets, you’ll still need to visit this sprawling, chaotic weekly flea market on the old Berlin Wall grounds between Prenzlauer Berg and Wedding – if only to watch the crush of punks and grannies mix it up for a day of Wurst munching, beer drinking, and bargain hunting.