Pope Francis is touring Poland through July 31, for the celebration of the Catholic church's World Youth Day.
Pope John Paul II established World Youth Day in 1985 with the purpose of inspiring youth to follow Christian values. The largest World Youth Day celebration was in 1995, in the Philippines, when 5 million people attended a Mass by John Paul II.
On his trip, the pope is visiting the Royal Castle and Cathedral in Krakow, a city that dates back to before the 10th century. Pope John Paul II lived in the city from 1938 to 1978, when he was selected as pope. The castle was home to the country's king until 1609, then centuries later ransacked during World War II. It has since been turned into a museum.
Pope Francis will also tour the Auschwitz-Birkenau death camp, which Nazis operated from 1940 to 1945. He will pray at the Death Wall and in the former cell of a Catholic Franciscan friar who volunteered to die in 1941 to save another man's life.
Both John Paul II and Pope Benedict XVI previously visited the Auschwitz memorial.
Pope Francis will also visit the Jasna Góra Monastery, Poland's holiest shrine. The monastery has an image of the Mother of God said to be miraculous. Hundreds of thousands of pilgrims come to the monastery each year to see the picture.
Other stops on the pope's visit include the University Children's Hospital in Krakow, the Divine Mercy Shrine and St. Faustyna's Chapel, the Sanctuary of St. John Paul II, and the Field of Mercy.
The Field of Mercy will be the location of the Mass on July 31.