The Secret Archives
The modern archives of the Holy See were established thanks to Paul V Borghese around 1610, but the roots of the history of the archives of the Roman Pontiffs reach way back in time, linking up with the very origin, nature, activities and development of the Roman Church itself. Right from the apostolic times, the Popes carefully preserved the manuscripts concerning the exercise of their activities.
This collection of manuscripts was kept in the scrinium Sanctae Romanae Ecclesiae that usually followed the Popes in their various residences.
Read all about it here
http://asv.vatican.va/en/arch/1_past.htm