Pope Francis made a pilgrimage to an Italian mountain town on Sunday and hailed the humility of a 13th century pontiff who resigned to live a hermit’s life, praising him for using his brief papacy to highlight the value of mercy and forgiveness.

Francis made a four-hour visit to L’Aquila, which was struck by an earthquake in 2009, killing 305 people and destroying much of the town, which is still being rebuilt.

The pontiff went to the Apennine mountains to give a boost to a late summer tradition begun by Pope Celestine V 728 years ago to encourage the faithful to seek forgiveness for their sins.

L’Aquila’s St Mary in Collemaggio Basilica contains the remains of Celestine, who resigned in 1294 after just a few months as pope.

As pontiff, Celestine initiated the August practice in which the faithful could pass through the basilica’s Holy Door. After meeting certain religious requirements, they can receive a plenary indulgence, which removes punishment for sin.

Aides took Francis in a wheelchair to the basilica’s austere, brown wooden door.

After Francis, who has a painful knee problem, was helped to stand, he used a sturdy olive tree branch to rap three times on the door, which then opened.

With a ramp put in place, he then limped into the basilica and prayed silently in front of the mausoleum containing the remains of Celestine, whose face is covered with a silver mask.

Celestine was ridiculed by Dante in the Divine Comedy for abdicating his papal role.

Francis said: “The humble appear to the eyes of men as weak and losers, but in reality they are the true winners because they are the only ones who trust completely in the Lord and know His will.

“Humility doesn’t consist in devaluating oneself but rather in that healthy realism that makes us recognise our potential and also our misery.”

He hailed the “courageous’ Celestine V because “no logic of power was able to imprison or manage him”.

Celestine reminded all that mercy and forgiveness help people to pass from “anguish and guilt to freedom and joy”, Francis said.

While the helicopter that flew him from the Vatican to L’Aquila earlier on Sunday morning kept circling above the town, with the pilot trying to find a break in the cloud so it could land, Francis said he was inspired to ponder the value of mercy.

“At a certain point, there was a break in the clouds, and the pilot zoomed through,” Francis said, encouraging people, when their lives are clouded by troubles, to take advantage of a ”break” when the possibility of mercy presents itself.

Before Francis, the last pope to visit L’Aquila was his predecessor, Benedict XVI, who went to comfort earthquake survivors in 2009 and paid tribute to Celestine.

Benedict resigned in 2013, the first pontiff in nearly 600 years to do so. He now lives in a monastery in the grounds of the Vatican.

Francis, who is 85, has called resignation an acceptable option for pontiffs who feel they can no longer adequately lead the world’s more than 1.3 billion Catholics.

He greeted local residents outside the town’s Duomo, or cathedral, which is still being repaired after the earthquake, and visited relatives of some of the victims.

Francis noted that inmates from area prisons were among well-wishers outside the cathedral.

“In you, I salute a sign of hope, because in prisons there are so many, too many victims,” he said.