The former royal residence emerged as the favoured location for the Catholic service on September 22 during a trip made to Berlin last month by Alberto Gasbarri, the Vatican's papal trip coordinator.
Vatican officials liked the fact that the palace grounds are open on three sides, which provides enough escape routes should they be needed.
In addition, the size of the area used for the mass can be easily adjusted according to the number of people estimated to attend. At the opening of the 1990 Katholikentag, a Catholic festival organized by lay people, some 40,000 people were in attendance.
The pope is said to have already agreed to the location.