quote:

Now that we've established our city, it is time for it to grow. Before we do, and since space is such a premium, it is worth mentioning zone stacking and how that is done. Since the manual covers it, I think the developers intended for us to play around with it. I also cover why I go with a grid layout instead of a doughnut block - especially on this tiny island. I apologize if the manuals are hard to read but these are the best scans I could find. I don't think my Nintendo Power strategy guide or my SimCity manual is in the best shape anyway.

The argument against doughnut blocks is mentioned here:
http://incise.org/advanced-sim-city-strategies.html