Runners competing in a half marathon pass the entrance of the John Paul II Cathedral Museum in Krakow in March. Over the past 15 years Poland’s middle class has seen its income more than double to €27,800. Photograph: Omar Marques/Getty Images Standing outside the orphanage run by the world-famous Polish medic Janusz Korczak in the Praga district of Warsaw, it is still hard to get your head around the fact that hundreds of children were taken from here to the Jewish ghetto across the river and from there directly to Treblinka, where they were all murdered the day they arrived....