There were twenty-four watches (mishmarim) of kohanim. Each worked for a week, from Shabas to Shabas, and then the cycle repeated itself. (Rambam, K'le Hamikdash 4.)
Was there only one city per watch of kohanim, or did a watch live in more than one city?
Was there only one watch per city, or did a city house more than one watch?
(Perhaps there was no correspondence at all between watches and cities. I have no reason to think there was one, except that travel to and from Jerusalem might be easier en masse and that twenty-four is half of forty-eight.)