Confrontation in the Vatican
After reclaiming the Apple of Eden from Girolamo Savonarola in Florence, and collecting all the pages of the Codex, Ezio Auditore da Firenze and the rest of the Assassins prepare themselves to learn where the fabled Vault lies.
I Came...
With all members of the order meeting in Mario's study at Monteriggioni, Ezio inspected what was written beneath the Codex Pages that was placed on the wall. He assembled them as members of the order look on, and successfully finishes, revealing the map of the world which showed the locations of other Pieces of Eden (41 in total). Ezio marveled that the landmasses depicted on the map didn't exist. Machiavelli answered that they did, but most likely had yet to be discovered, "or rediscovered" as he added.
To Ezio's shock, he then saw that the much-talked-about Vault was located roughly where the city of Rome stood. It was then that he theorized that Rodrigo Borgia became Pope so as to get his hands on the Staff. When Teodora questioned Ezio's meaning, Mario Auditore explained the prophecy from the Codex, stating that two Pieces of Eden were needed to open the Vault, one of the Apples and the Staff. The other Assassins began to speculate about what the Vault would contain, and expressed their fears of what Borgia would do once he had attained it.
Ezio opted that he would confront Borgia and try to open the Vault himself. The other Assassins agreed, offering to "cause trouble in the city" to keep the Borgia guards from stopping Ezio. His mission planned, and with final vengeance in sight, Ezio departed for Rome.