I'm looking for a word that would carry the same connotation as "Private Realm." If you can think of a good word, you can skip the rest of this.
I'm working on some architectural projects where I'm contrasting publicly visible and accessible space (whether publicly owned or not) and private space not visible or accessible to the general public.
I've decided to call the public space "Interface" -- people seem to understand this and they don't get sidetracked arguing about whether privately owned plazas etc. are "public".
I'd like to pair Interface with a single word that indicates private space, places that are not necessarily intimate but are simply not public. Basically I'm describing the difference between a front yard and the living room in a house. The front yard can be described as interface -- it's a public space (privately owned), and also a connection between the public realm and the private realm. The living room is private space. If someone walked through your front yard it wouldn't be a big deal -- if someone just walked into your living room it would be a big deal. See the difference?
It would also be fine with me to coin a new word as long as it sounds good next to "Interface" and as long as it doesn't trigger negative associations.