Castle Rock is the location of Shawshank State Prison in the TV adaptation https://castlerocktv.fandom.com/wiki/Shawshank_State_Prison
There are a few posts where Q simply states:
'CASTLE LOCK'
... instead of CASTLE ROCK, maybe locked up?
So maybe that's a reference to prison.
So maybe it’s referring to GITMO?
Oh yea, I just saw the before and after pictures today.
Lotta works been done there over the last 4 years!