On the south side of the atrium, going towards the tablinum, there is room 3. I couldn’t find any sign of the existence of a door (pivots etc...) but, of course, it does not mean that there wasn’t any.
Some bits of the floor made in opus signinum (or cocciopesto) are still visible and they show traces of a nice decorative pattern of white tesserae. There are no windows at all, but the room is open on the atrium. So far, I have no hypotheses about the use of this space. It looks like it is facing a similar one on the other side of the atrium (room 6). Is it possible that the two rooms were functionally or visually related?