I think he's cryptically speaking of Rome.
This would have been about the time of that crazy Nero who viewed Christians as his worst enemies, so of course Peter would have been wise not to reveal their actual location.
Also, Josephus reports that all the Jews had left Babylon by the time Peter wrote his letters to the Jewish Christians.
The WT doesn't want Peter in Rome because this weakens their argument that Peter wasn't the Rock to whom Jesus referred in Matthew 16.
Doesn't it feel great to be able to research for ourselves?
Blessings.
Sylvia