I specifically visited Kraków so that I could go to Auschwitz-Birkenau (it was as depressing as you'd expect), and was pleased to find the city thoroughly charming, and quite busy at the end of winter.
The Auschwitz concentration camp entrance gate with the sign "Arbeit macht frei" or "Work makes you free" (a replica of the original sign, which was stolen in December 2009, and since recovered, cut into three pieces)
Auschwitz electric fence
Birkenau extermination camp: end of the line (I could not believe how many tourists were getting their photos taken, draped across these train tracks)
Birkenau gas chamber destroyed by German troops as the Soviet forces approached in November 1944
Guard tower with Birkenau camp buildings in the background
Wawel Hill featuring Wawel Castle, Kraków
Dominican Church, Kraków old town
Church of SS Peter and Paul, Kraków old town
Town Hall tower, Rynek Główny (Main Market Square), Kraków old town
St Mary's Basilica, Rynek Główny
Florian Gate, Kraków old town
Old city walls extending from Florian Gate
Courtyard of Collegium Maius, the oldest university building in Poland
Next: Budapest, Hungary...