Father Gaspar noted that the door being used is the one that connects the choir chapel to the main chapel -- a door that the sisters pass through every day -- but "the door will now take on a special significance," he said.

The ceremony began with the sisters assembled in their choir chapel as Father Gaspar sprinkled the door with holy water and blessed it. Following other prayers, the Holy Door as was opened and the sisters passed through it to the side chapel where they attended the Mass celebrated by Father Gaspar, separated from visitors by a grate.

"The Holy Father really is an amazing man," Father Gaspar said in his homily. "He wants to show the world that our God is full of mercy, full of love."

"To pass through this door of mercy is to remember ... the Passover. To pass over -- to pass over from a situation of sin and death to a life of love and grace," he said, adding it is a reminder "to leave the darkness behind."

Father Gaspar went on to explain that although the Church has been criticized for selling indulgences in the middle ages, Pope Francis has made them available to all.

"Pope Francis wants to show everyone that indulgences are very freeing," he said. He noted that for those who cannot go to the cathedral to pass through the Holy Door -- for the incarcerated, the ill and homebound, and for those living in cloistered monasteries, the Holy Father has made accommodations.

"This indulgence is freely given to all," he said.

"This is a year to experience the full extent of God's mercy," continued Father Gaspar. "We are called to be a people of mercy, to experience His mercy and, in turn, give it to others."

Sister Mary Veronica, OSC, vicaress of the convent, said she was very moved by the experience.

"I really feel that this Jubilee year will be able to break some of the barriers people who have left the faith have built around themselves," she said. "[Pope Francis] shows us really that God loves us, how much He loves us and how much He wants us to remain close to Him."

Sister Mary Veronica also praised the pontiff's decision to open the Holy Door within cloistered convents.

"That's the kind of Pope he is -- he thinks of all of us. And for those of us who stay home and pray, that really means a lot," she said.

"I hope God blesses him with a long life," added Sister Mary Veronica.