we modeled ours so that you had large 4m chunks that could be further subdivided down to 1m for detail, so long as you stick to the same grid you can fill in the floor and build custom geometry for areas of interest and detail.
A few chunks, the easiest way to create levels in max was to turn object snaps on and just SHIFT drag them by a vertex to clone/instance them around snapping to another adjacent vertex on a neighbouring tile. since the whole thing has pretty simple lighting wise it can be a good idea to use quite a high polycount so that your blitz vertex style DX lighting is well defined.
A few chunks, the easiest way to create levels in max was to turn object snaps on and just SHIFT drag them by a vertex to clone/instance them around snapping to another adjacent vertex on a neighbouring tile. since the whole thing has pretty simple lighting wise it can be a good idea to use quite a high polycount so that your blitz vertex style DX lighting is well defined.