The Town Hall construction commenced about 1299 and continued for the next 250 years.  Much of Wroclaw was destroyed during WW2 and the buildings around the market square have been restored.  Took the free walking tour which lasts several hours.  They are offered in many cities and we have found them to be very good - give the leader whatever you think the tour was worth.  The Jesuit University was built outside the original walled town as by then the country was Protestant.   Student protest started in this city before Solidarity in Warsaw.  The student action was mainly kept light hearted and resulted in a "gnome" action - small gnomes put at various locations which originally made fun of the communist regime.  Now there are some 400 gnomes round the city.

Auschwitz is a short drive from Krakow.  It was established as a camp to deal with prisoners of the state and quickly became the processing point for the new camp down the line, Birkenau.  Auschwitz contained not only  Jews but also "political prisoners" such as captured Russian soldiers, Gypsies, those considered criminals, those considered likely to escape, homosexuals, exponents of the bible and those considered anti-social. This included not only Poles but those from countries as far away as Greece.  A political prisoner could be as young as 12 and some that age were charged, convicted and shot. 

Through these camps:
1,100,000 Jews - 1 million perished
150,000 Polish prisoners - half perished
23,000 Gypsies - 21,000 perished
15,000 Soviet POW - most perished

Auschwitz was a series of buildings with pleasant accommodations for the Nazi officers and their families.  Birkenau was a camp originally built using stones from several demolished villages.  When the stones ran out they built row after row of timber buildings to house the inmates - who were not expected to remain long and never expected to leave.

The crematoria were dynamited before the Nazis left and many inmates were shipped out or forced to walk as the Germans retreated in front of the Russian advance.  All you need to remove a few million people is some pesticide, a few not large crematoria, and no objections.