In my mind I have the view of how the main planet will look but I lack the skill to draw it out for you. So I shall try to describe how it looks the best way I can.
Think of the toy top
The top half will also have huge mountains like the bottom but not as rugged. As there is an atmosphere that we know the world looks round from a distance. So unlike the above image there is air on the bottom half.
Center of its own Universe
This will be the center of the universe as I will build around it and make things as I see fit. I will need to work in on how the sun and all that work but it will have a place but it a world of magic anything can go.
Well that is what I have thought up and will have more soon.