Only thing I know about Kraków is they run the auschwitz tours from there,I've done that,it's worth going to see,the rooms full of belongings from the last week of the final solution,bring home the scale of death that occurred.
The auschwitz side of it is done at a brisk pace to get the amount of visitors through,you enter a gas chamber which is chilling to say the least.
The birkinau side of it I enjoyed more(wrong phrase but you know what I mean)it's a better pace,a lot bigger,you see the old crematorium,and they take you around a barrack/living block as well.
On another grim note,if you ever find yourself that way,the genocide museum in Vilnius is proper spine chilling,you get a pre-recorded guide and are allowed to walk around on your own,the building at one time has housed the nazis and the KGB,and there's lots of bricks on the outside of the building with a name on,in memory of a person who died inside,I'm not going to give the twist at tours end away,just that it really leaves you shocked and numb