...and it is not too expensive to spend there few days. I think the most spectacular are early spring and autumn when there are very photogenic fogs. You should think about visiting this place during this time
Unlucky Poland looks like most european countries. Agriculture and industry changed most of its teritory. Luckily there are still many areas with natural landscapes, some of them are unique like Bialowieza Primeval Forest (on UNESCO list) or Tatra Mountains and Biebza swamps. Mountains are my fav place but I visit often Mazury Lake District, because I have my family there and there is my university field station.