I have created a mountain in 3DS Max for use in my game. It will be used not only for the background, but also as a 3D world that the avatar climbs and enters/exits. The mountain is currently 200' by 200'. My question is how big should I make it in order to be able to create paths on the outside as well as be able to zoom out and see the whole mountain but also zoom in to each outdoor level which then becomes the 2d side scrolling level.

Any thoughts on the size of the 3D mountain Model for this design?