Old Town (Stare Miasto) in October

May through September gives you the best weather and longest days — crucial since Old Town really shines during golden hour. July and August bring crowds but also street performers and outdoor dining. September might be perfect: warm days, fewer tourists, and the light hits those reconstructed facades beautifully. Winter works too if you don't mind bundling up — the Christmas market in Market Square runs December through January, and snow on Gothic spires looks pretty magical. Just know that some restaurants close early in winter months.