Pope Francis exited his popemobile to visit a "knot grotto" that is based on one of his favorite paintings and lets visitors acknowledge the challenges in their daily lives.
The installation built next to Philadelphia's Roman Catholic cathedral is inspired by a painting called "Mary, Undoer of Knots" that holds special meaning for the pope.
The artwork at Cathedral Basilica of Saints Peter and Paul shows Mary untangling a long ribbon -- a symbol for smoothing life's difficulties.
The painting hangs in a church in Augsburg, Germany, where then-Rev. Jorge Mario Bergoglio saw it while studying in the mid-1980s. He brought back copies to Argentina, where it became a major source of devotion.
People were invited to write down their own problems on ribbons tied to the grotto. They were also encouraged to help others by loosening and removing a knot already in place.