Pope Francis walked alone, in silence and painful reflection, through the infamous Nazi concentration camp.

A merciful heart, Francis said, is one that “can welcome refugees and migrants.”

Francis spoke to more than 300,000 Poles at the famous shrine of the Black Madonna.

Francis said there is a need “for great wisdom and compassion” in addressing “the complex phenomenon of migration.”

For some time now the pope has spoken of a world war “that is taking place in pieces.”

The presence of John Paul II, who began the youth festivals in 1984, is still strong in this Polish city.