Steel General, that's very close to what I was looking for. The sky and ground below is awesome. The layout of the land is great. Based on your description, it's practically the same idea, except yours is a floating castle.

If you were willing to modify it, the castle would have to be removed -- otherwise that would be the world's biggest castle (since the earthmote is 2 miles in diameter). Then just add smaller-scale terrain and it would be an overland map.

That's a really nice map.