That is a strange request for a cake, isn't it? Depending on how big you need it, I would suggest that either you get three slightly different sizes of ball cake pans and then slice off the tops and bottoms and stack, or else you'd need to bake three rounds and carve each into shape.
I'm not sure how best to cover it with fondant to make it look all one piece. The easiest thing would be to cover each tier individually and then try to just smooth it together once they are stacked, but if it's not too big then you could attempt to do it all in one go.
If you want the level of detail then you could use an apple corer to make a hole down the middle.
Hope that is of use!