CZESTOCHOWA, Poland — Pope Francis, visiting a shrine cherished by Poles, praised native son St. John Paul II on Thursday as a “meek and powerful” herald of mercy, and honored the countless “ordinary yet remarkable people” in Poland who held firm to their Catholic faith throughout adversity in the former Communist nation.

The Argentine pontiff, who had never had set foot in Eastern Europe before this week’s five-day pilgrimage to Poland, gazed in awe for several minutes as he studied the Jasna Gora monastery shrine’s iconic image of the so-called Black Madonna. The faces of Mary and Baby Jesus in the icon are blackened by centuries of varnish and candle soot since the artwork became the object of veneration starting in the 14th century.

A silver screen was raised slowly and dramatically to unveil the image as Francis stood silently in admiration and then prayed.

Then, during an outdoor Mass in the southern city of Czestochowa, before a crowd that appeared to number more than 100,000, Francis lavished praise on Poland’s steadfast Catholic legacy as he urged Poles to hold fast to their faith.

As Francis walked up to the altar he tripped and fell over, but was quickly helped to his feet by others. He went on to deliver a long sermon and a Vatican spokesman, Greg Burke, later said “the pope is fine.”