Walk the riverside
It's a nice walk along the steep bank of the vistula river. go to the city hall, then move southwards till you reach the promenade on the bank. if you choose to go down the steps, you can walk at the bottom of the steep slope and walk past the rock-like forms of the sandy cliffs that are located in the direction opposing to the two vistula bridges. another option is to remain atop and stroll westwards on the top of the cliffs. nice views are guaranteed.
entertainment
"Reggaeland" (http://www.reggaeland.eu), the second largest reggae festival in Poland. Professionally organized, 3 scenes reggae, ragga/dancehall, raggajungle, good artists, nice vibes. Reggae festival takes place on the very river bank, in mid-July.