For administrative purposes, each of Isarn's Districts is broken into several sub-districts known as Quarters; whether by planning or by happenstance, this results in a nice round fifty. Four Districts are considered subdivided before Quartering, as follows:
Each Quarter has a name*, and when giving an address, residents will often give the District and Quarter as part of it, such as '34 Place des Invalides, Contentieuse', in order to better orient their conversational partner as to where in the city the address is located. (This helps visitors less than you'd think it should.)
La Rouille is, for administrative purposes, considered part of Le Commune's 1st Quarter.
Each of a settlement's stat blocks are added to certain rolls, as follows:
These apply to all appropriate rolls, whether by you or by an NPC; obviously, the 'Danger' stat is essentially GM-only. If you are using Hero Lab and have ShadowChemosh's Adjustments, you can apply a 'Skill Bonus, Situational' for each of these, and that'll show up on your sheet in the correct places.
* - Due to Cultured, Isarn is always considered to be Prosperous (+1 to Economy) for the purpose of certain checks to generate income; briefly, the check has to create or express something 'artistic' in the 'high art' sense of the term -- statuary, paintings, opera, drama, orchestral music, and the like. Street musicians play the lute and sing arias and solos, or band together and perform 'chamber music' and the like. 'Low' art -- bawdy comedies and music, farcical plays, street art/graffiti, and similar activities, fiddlers with monkeys -- do not receive this bonus, but do not receive any penalty; the point is the people appreciate the 'high art' more.
* - The names of the 50 Quarters of Isarn have not been established, in part because while Isarn is modeled very closely after Paris, some of those Parisian Quarters outlines are crazy. As well, while this Isarn's map is more closely modeled after Paris, it does not have twenty arrondissements, each broken into four quarters, for a total of 80. Players are encouraged to come up with names, which will eventually be added to each District's page.
As well, Eponine d'Ambreville draws a harrow card to determine which district La Marquise is going to haunt each night she goes out; if we can work together to get district names, a small sense of the neighborhood (as appropriate to its District, sites found therein, and its location otherwise), and perhaps offer potential card matches to each Quarter, that would be helpful.