The Pope “will go on a pilgrimage to the Shrine of Our Lady of Fatima from May 12 to 13,” the Vatican announced. The pilgrimage will mark the anniversary of the Marian apparitions, which first began on May 13, 1917, when three shepherd children reported seeing the Virgin Mary.

The apparitions continued once a month until October 13, 1917, and later were declared worthy of belief by the Catholic Church.

Pope Francis will be the fourth pontiff to visit the Marian shrine, following the footsteps of Blessed Paul VI, Saint John Paul II and Pope Benedict XVI.