Travel / Vacationing in Krakow for a month, how to keep myself occupied? [9]

Already done all the usual tourist activities so what's next? I only know a handful of people here, so far all we've done is go sit in the rynek and drink beer. Im staying with a friend who he works everyday and usually brings me along, kind of strange if you ask me. I'll usually break away for a few hours and go for a bike ride or like today just went for a run by the river (the highlight of my day). Only other people i've met have been students so they're obviously busy during the days. Any other ideas for things to do?