Spent my stag there, best weekend ever. Get to the backstreet bars just off the old square, where the students hang out, many have a relaxed retro vibe with lovely cheap beer. The locals are reluctant to talk at first but if you go out of your way to talk to them they soon open up.
The exotic dancer clubs are certainly easy on the eyes too.. Perfect 10’s abound.
You can barter a good deal on the open topped cart tours of the city, which will take you around the Jewish quarter and schindlers factory, well worth an hour or twos relaxing if nursing a hangover. Further afield you can visit the salt mines and go gun shooting fairly easily.