The altar where Pope Francis will celebrate Mass in Revolution Square in Havana near a government building decorated with the likeness of revolutionary hero Ernesto "Che" Guevara. The Mass is scheduled for Sept. 20. Desmond Boylan/AP hide caption

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In this image taken from a video provided by Adnkronos International, Ali Agca stands in front of St. Peter's Basilica at the Vatican, on Saturday. Agca, who tried to assassinate Pope John Paul II in 1981, laid flowers at the late pontiff's tomb. AP hide caption

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Pope John Paul II at Giants Stadium in New Jersey in 1995. John Paul, the pontiff from 1978-2005, was a favorite among traditionalist. He will be canonized on Sunday along with the late Pope John XXIII, he was popular among liberals. David Ake/AFP/Getty Images hide caption

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Tapestry portraits of Pope John Paul II (left) and Pope John XXIII hang from balconies on the facade of St. Peter's Basilica in Rome. On Sunday, the two pontiffs will officially be declared saints. Claudio Peri/EPA/Landov hide caption

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Tourists walk past a poster of Pope John Paul II on April 13 in Rome. Gregorio Brogia/AP hide caption

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