There are a great many guided tours to do, both in Krakow’s city centre as well as on the outskirts. For instance, on full day tours, you should visit the wonderful Salt Mines in Wieliczka and the sombre but must see Auschwitz-Birkenau.
In the city centre, there is the Kazimierz which is the former Jewish Quarter and the Old Town, and these are the two main sections. Each with amazing attractions including the former Royal Castle, Wawel, between them.
Another plus for the city of Krakow is the nightlife as it is reported to have the worlds highest density of bars!