"They came during the centuries, but now this is their home," Monsignor Pasini said.
"There's one person who can actually take a book out of the library, correct?" Safer asked.
"Yes, the pope can have every book in the library," he replied.
If Saint Peter's Basilica represents the splendor of the church writ large, the library nearby is a testament to the monks and scribes who made magnificent miniatures in times past.
For example, preserved is a manuscript of some devotional music commissioned by Pope Leo X. And there's the text of the Christmas Mass, used at the altar by Alexander XI. Both manuscripts, five centuries old, are written on parchment -
treated animal skin.
"You will often see the skin of sheep being used, sometimes goats," Christopher Celenza, director of the American Academy in Rome, explained.
Celenza is a scholar who has often used the library. He says that writing on parchment was not only tedious, but expensive.
"If a monastery wanted to produce a Bible that perhaps had 400 pages, it might cost you 400 sheep, if you're a monastery. So, it's an investment," he explained.
"Beyond the academic work, did you ever just come here to hang out and flip through stuff, and see what you might discover?" Safer asked.
"I think all of us have come here at one time or another with the hope of discovering something, having a general direction in which we're going, but not quite knowing where we'll wind up," Celenza said.
Or, from an 11th century treatise on the art of war, an image of a Byzantine soldier brandishing a flamethrower - something the Greeks invented 1,500 years earlier.