It is named in Lucia's official background as where she was held. Named locations in character bios have a decent track record of being real places you can go.
Question is whether it is somewhere the story takes you and nothing more, or whether it sits on the map as a permanent location with a wanted level attached to being near it. Those are different design decisions and the second one is more interesting.
a prison you can see from the road that you know she was in is worth more than a prison you can walk around in honestly
Agreed. A building with meaning attached does not need to be enterable to do its job.
Named locations in character bios have turned up as real places before, though not always as somewhere you can enter freely.
That is a better answer than the one I was fishing for. Presence beats access.
Reading this after the showing and I would add that a prison on the map with a wanted level attached to being near it is the sort of detail this game would absolutely do.
Whether the story goes back there is the actual question and it is exactly the kind of thing I do not want answered before November.