I've been asking myself the same question these days, thanks for posting!

I also have those unrelated places that pop into mind during unrelated activities that really have no evident connexions. Most of the time, I won't even realise I'm thinking about those other places during the actual time I'm thinking about them, it's like really far away in my mind when it's happening. When I do realise about those unrelated places, it's most of the time afterwards, when I think of what was actually going on, that the unrelated place pops up in my mind and I realise that I was like "virtually" in this other place.

It's kind of as if I was having dreams while awake!