no all the cities are 2kmx2km
http://www.ign.com/wikis/simcity/Cape_Trinity
cape trinity is the zone that was in the beta, 3 cities that are 2kmx2km and 1 great works area. Clear water was the beta zone you could actually build in.
So... there are regions that are smaller that cant hold 16 cities, yet city size is still only 2kmx2km... that just seems pointless to me, from a multitude of perspectives.
But, it is what it is, I guess.