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FATIMA, Portugal (CBSMiami) — Pope Francis and up to one million pilgrims are in Portugal to celebrate a special anniversary at one of the Roman Catholic Church’s most sacred shrines

Pope Francis greeted young children on his arrival in Portugal. The Holy Father walked down a long receiving line, paying extra attention, as usual, to kids with special needs.

The pope is celebrating 100 years since the Virgin Mary is said to have appeared at Fatima before three young shepherds tending their sheep. The children said the Madonna urged them to pray for peace and turn away sin. Catholics consider the appearance one of the most important spiritual events in the 20th century.

Outside the shrine in Fatima, another huge crowd of pilgrims gathered to see the pope.

Pope Francis prayed silently before a statue of the Virgin Mary and urged followers to make God’s justice and peace known.

On Saturday, the pope will make two of the shepherds saints during a special canonization mass. The 3rd shepherd is still in the process of becoming a saint.