A great concept that many may be familiar with from other European cities. All you have to do is show up at the right time in the right place and enjoy a walk around town accompanied by guides who are truly passionate about it. If you love it (and you most likely will), you can tip the guide at the end of the tour according to the 'pay what you want' model.
Free Walking Tour - Main Town Gdansk
April - September: every day at 10 a.m. + 11 a.m. Fiday - Monday
June - August: daily at 4 p.m., in addition to the above