Holy Years normally take place every 25 years unless a pope decrees an extraordinary one to bring attention to a particular need. The next one had been scheduled for 2025 before the pope called for a special one on the theme of mercy, a major part of his push for a less judgmental and more inclusive Church.
. Pope Francis, (C), kisses the altar as he celebrates Mass.
During the year-long celebrations, one of the most important traditions is pilgrimages to Rome and other religious sites around the world by faithful.
. Italian police officers search a nun at the entrance to St Peter's Square.
. A woman takes a photo prior to the start of Mass.
. Priests take shelter from the rain as they make some final adjustments near the altar ahead of the Mass.
. A Vatican employee pours hosts into a chalice to be given to faithful during communion.
. Pope Francis spreads incense around the altar.
. Pope Francis pushes open the Holy Door of St. Peter's Basilica, formally launching the Holy Year of Mercy.
. Pope Emeritus Benedict XVI, (C), is helped to pass the Holy Door as Pope Francis looks on, during the ceremony.
. Faithful wait for the start of Mass.
. An Italian fireman climbs a ladder to lay a wreath of white flowers on the Immaculate Conception's statue.
. Pope Francis opens the Holy Door.
Read More: Pope Francis Launches His Holy Year of Mercy