Several places in Europe are not just cities, and others just castles, and others just bishops, several places like Paris had a city, a bishopric and a castle within it, like London and York, a better system would be, you Count of York may well make York a walled city as a residence rather than strictly a castle, or it may well have a castle with a city around it, where her mayor would live in his court. This system of separating castles, cities and bishoprics is very unrealistic. Cities have always been a densely populated and highly complex place, not only a trade-focused village governed by a mayor, they always held a bishopric, or a fort, in or on the city side, of course that does not take away the fact that grand castles within the regions functioning as forts, but that does not detract from the fact that the noblest kings of a country had their residence in a city complete with bishopric, fortifications within and around the city.