The City of Anuire is the ONLY city I know of that is it's own province. The 3E rules mention a city as a province, but do not go into details.

So I thought we might want to.

Am i missing something?

OK, so here is my thought on this. Once a Province level goes above the normal maximum for the terrain type, then then a city in the province can become it's own province. There are more conditions though.

-The province must have no more room to grow (a it's maximum level)
-The Province must be fortified up to it's maximum level.
-The City must reside on a coast or on a major river (both for City of Anuire).
-The City must have at least 3 Trade Routes going to it.
-The City must have a Seaport.
-A Decree must be made Declaring the City independant of the province.
-A rule action must be made to increase the province level by one, forcing the province level above what is normally allowed. If this rule action fails, the province level does not rise, and the city remains part of the province.
-If all these conditions are met, then the city can become it's own province.

The new province level will be split 70/30, with 70% of the level going to the city, and 30% to the surrounding province. Round any fraction up for the city and down for the province, but the total of the 2 levels must match the new province level. This leaves room for growth for both, and doesn't ignore that not everyone would live in the city.

This hasn't happened in any of my campaigns, but I thought it should be addressed, because it might in the future.