I just took a peek at the December issue and I'm embarrassed. I've been trying to figure out where the 15" separation of levels comes in and now I know. Somehow I missed that this layout will extend down to the floor and the base is just that, a base. I've been waiting for the "table" to be flipped over and the 2nd level added.
After seeing the article, I'm amazed at how much landscaping will need to be done to cover this floor level railroad "island". I've seen layouts with some sections extending to the floor, but that the entire layout. I'll be watching to see how it all turns out. Based on what's been done so far, I have no doubt the result will be exceptional.