People-watching and treasure-hunting
I stumbled upon the Boxhagener Platz one Sunday afternoon, trying to kill some time before catching a train to Hamburg. On Sundays between 10am and 6pm the square is home to a colorful flea market selling mostly arts and crafts, many of them homemade, but also some antiques and just random stuff. There is usually life music as well, on at least one end of the square. Once you have grown tired of exploring the market, you can sit down in one of the many cafes around the square, which is a great way to relax and watch, especially in summer with most cafes having tables outside.