I've been looking at specialising my cities more, so gear them completely for production or commerce, this is ok, now my task is to reduce the number of improvements i build. A question for some better players. what cities do you consider your core? the first 5? 10? 15? and how far beyond that do you go before specialist farming? i generally just use the continent as the divider but does anyone have a decent guideline for how far from the capital the core stops and where the farming should begin