I see my last post would probably give rize to more questions then answers so I'll add the following:

The structure dictates the order: region - city - district

Since we've got two continents to play for, this could and would never work. So we opted as follows:

region (first we had the four directions, but opted for one region meso-america, with aztec and maya cultures in mind)

cities not as cities but as regions, based on geographical boundaries

and finally the districts as being the real cities

I understand this still leads to confusion, not in the least to me *s*