The last time a pope entered Notre Dame Cathedral was in 2008. It was during Benedict XVI's trip to France where he visited Paris and Lourdes.
In this historical Gothic cathedral the pope knelt before the relics of the crown of thorns. Along with other historical items, it was saved from the fire in the cathedral on April 15. He also prayed vespers together with nuns, priests and deacons.
BENEDICT XVI
“The faith of the Middle Ages built the cathedrals, and here your ancestors came to praise God, to entrust to Him their hopes and to express their love for Him. Great religious and civil events took place in this shrine.”
Benedict XVI visited France for the 150th anniversary of the apparitions in Lourdes. Even today the pope emeritus prays near to a Lourdes statue of the Blessed Mother in the Vatican gardens.