Yes, you're right. The bathrooms take up only a section of the building. There is a cafe/restaurant on the oppositve side of the building, and probably there are more rooms not open to the public, as it is a very large building. I think it is the high roof line that gives the impression of being three stories. Yes, there might be a rather tall attic in there.
btw, when you went to Belle Isle the other day, did you check out this picnic area [[across the road from this building)?
Bookmarks