Oh boy, Dream Central!
What others have said, Moondreamers was another line by Hasbro in 1985/86. I'm sorry my ID site is down at the moment or I'd link it, but what that is is the biggest playset for them, it would be the equivalent of the Dream Castle for MLP in terms of size, maybe a bit smaller since it doesn't unfold quite as much. The cool thing about the Moondreamers line is that it features glow in the dark parts and accessories. I've got a lot of the accessories myself, but haven't run across the building yet.
I'm sure there would be someone interested in trading or buying it from you (such as Elisto, lol).