Although typically associated with social strata, this refers to the literal layers of the city that one finds in most places.
Where the most elite citizens typically live, the pinnacles of the city jut up into the sky where they are lit all day long by the sun, and are never in shadow.
Near the pinnacles, these places can look down on the “roof” and open “streets” of the city, and are only in shadow when a pinnacle casts it's shadow upon them. Which can be considerable, if right under a pinnacle, and on the wrong side. The well to do usually live in these regions.
These are buildings and streets that have nothing directly above them, but are generally overshadowed much of the day by the heights and pinnacles, and the bridges and other infrastructure that may connect them (which will some day become the new roof when they grow together). Often this is the cite of the educated professional classes of the city. Those who live on the rooftops - and certainly those above them - enjoy meals most often at home prepared by servants who go to get food on a daily basis. It is simply usually too difficult for denizens this far up to go to the farms to get food for themselves. There are some few shops and markets that exist on this level by buying food from the farms and reselling it to the people this far up.
Just under the rooftops these places can get occasional light through skylights, but even then it's somewhat rare, depending on the specifics of the location. Often the abodes and workplaces of artisans, or those who practice trades or crafts. Note that the roof slopes down where it comes near to a farm, merging to become part of the chasms effectively. These places are often as sought out as the Rooftop is, or even the heights, because some times the views across a farm can be quite amazing.
Below the roof, but with occasional ability to have light seep in through crevices in the roof, this level is almost dark, almost all of the time. Commoners and laborers who work for the people above find these places home, if they're lucky.
Where light finally fails is where the a large proportion of the population lives in something approaching poverty. The Warrens are, at least, mostly devoid of sewage flow, or bodies or the like, and the rats here are not too much of a nuisance, if ever-present. Everyone in the warrens on down goes to the farms directly for food, often going there daily.
Below the Warrens are areas that start to become abandoned, as they do not have much access to the upper layers, and usually one can find housing in the Warrens if nowhere else. That said, the dispossessed of society reside in the Underneath, because they are not wanted, even in the warrens. Sewage begins to pile up in the Underneath in places, but usually it is routed to the depths below. In many places the Underneath gives out directly to the ground level where the farms are, and those who live near this border actually have quite a convenience. Again, right where the Underneath gives out to the farm opening is better thought of as part of the roof layer in terms of how sought it is.
A big layer, these are areas below the Underneath, where almost nobody lives, except for the occasional hermit. I some cases, the Depths may even go under ground level (though it's often very hard to know this for sure). The depths are an awful place that people avoid unless they have a job that takes them there.
Some few have explored the Depths in places enough to know that one can go even further down. Or so they say. Rumors of huge serpents that live off of waste, demon caverns, corpse-eating humanoids, fungal forests, and even ancient gods buried here are surely just that… rumors… This layer, if it exists, is definitely below ground in most places, and who can say how deep the deeps go?
The city is so large that only a handful of organizations can be said to be truly found everywhere.
The office of the Mayor is a position of almost zero authority. In a very theoretical way, the Mayor constitutes a central authority of the Great City. In practice, however, the individual feudal lords of the various neighborhoods of the city control their parts of the city, and pay the Mayor no heed. In fact, in practice the lords use the Mayorality as a scapegoat, or a place to shove off problems when they don't want to solve them.
This is very inconvenient for the person so shoved, given that the Mayor has no single residency. Instead by perceived necessity the Mayor travels around the city, going from neighborhood to neighborhood, in an attempt to be able to speak with the citizenry and address their issues. So finding the Mayor at any given time may require some investigation and extensive travel across the city. And few bother, since the Mayor has no real power to effect changes. They Mayor may remind a local lord of their duty to the city and upholding a fair rule, but it's up to the lord to actually address any issue. If the Mayor's suggestion is inconvenient, the lord in question usually just says that they'll take the suggestion under consideration, and then forget about it after the Mayor leaves.
Mayors who have gotten out of line have frequently been assassinated, and it's not a very sought out position. The position has no salary, but most Mayors make a reasonably good living through accepting bribes for the minor favors that they can give out. And since they always have a food and board provided by the lord with whom they are currently visiting, they don't have much in the way of expenses. That said, one of the real reasons for the Mayor's nomadic nature is that they fear to stay too long and annoy the lord who currently houses them. So best to move on to annoy another lord before being assassinated.
Given all this the job of the Mayor tends to change hands very frequently. As such, no description of the Mayor is given here, allowing the details of the current Mayor to be made by the GM if and when a visit occurs. Not all Mayors are weak-willed dupes; although this is the common stereotype that people have of what a Mayor is likely to be like. Occasionally a strong Mayor comes along who acts with some sort of integrity. This does not change the fact that they have very little power, and that no Mayor is ever likely to have much.
The Mayor theoretically has power in the form of the City Guard. Like the Mayoral offices, it is traditional for lords to create a guard hall somewhere in their district (the Architects are supposed to create such free of charge as part of their mandates), and to pay to keep guards stationed. In practice, the lords usually do not pay very much, meaning that there are very few guards, and they are very poorly motivated. That, or the local lord pays them under the table to be just another arm of their own power-structure. Those that don't pay off the City Guard usually have even more powerful personal guard regiments.
Because of this, going to the City Guard to get justice is a dodgy proposition at best. Most never bother, and instead go to whatever powerful patrons they have for protection and redress of issues that they may have.
The city could not exist in its current form without the existence of the members of the Architect's Guild. Architects perform the extremely complex arcane art of constructing buildings with magic. Materials have to be brought in for them to assemble, but not nearly as much as if the buildings were built in a mundane manner; meaning they can build in the claustrophobic precincts of the city, even atop other structures.
The powers of the architects are entirely constructive, they have no means of demolition. And the structures they build are impossibly strong. As such, few even attempt demolition before starting a new project. Far easier to simply build atop an unwanted building than to try to destroy it to create space. Further, since this began, the city has climbed ever skyward, and building at low levels would mean being in the shadow of other places. So the city just keeps being built up, layer upon layer. This has been going on so long that none are very sure how deep the depths of the city go. Most of the sewage systems built into new buildings simply drain down to lower unused levels somewhere, as does rainwater runoff. Meaning the bowls of the city are often dripping awful places that nobody goes. In the earliest days the architects even built down into the earth, meaning that even where you find “Ground level” this may not be as low as you one can go.
There are, in fact, places where one can reach the earth easily, however, places where the architects are mandated to build so as to allow light to reach to the lowest parts of the Great City… the farms…
Like the Architects, the Harvesters are a caste of people without whom the city could not exist in its present form. The Harvesters are capable of creating huge supplies of food for the city by growing new crops of food every single day. They operate from “Farms” that dot the city. These open areas of substantial size can be found at least one to every neighborhood, sometimes more. They all take similar forms, a “dent” in the skyline of the city that the architects must arrange to be sure that the sun hits the ground by 10 AM on a winter day. The fields themselves are typically surrounded by a two-story ring of buildings that form a wall, into which are built all sorts of bakeries and market stalls, taverns, even restaurants.
Each lord is held responsible by his citizenry for ensuring the proper operation of the farms in their precincts. A lord who somehow mismanages their farms is likely to end up lynched in very short order by a populace who is well aware of what happens when the farms fail. This does happen with some regularity here or there about the city, and the results are always a wave of refugees that pours from one part of the city to the next, resulting in rioting, looting and many dead. This also means that lords pressure each other to ensure proper operation of their farms, so as not to have to deal with issues should a farm fail in a neighboring precinct.
That said, the lords do not have direct control over the farms, but merely facilitate these operations. The farms themselves are peopled by a the harvester caste of people who live in little rural villages amongst the fields. They are a close knit folk who do not like city folk getting inside the “walls” of their farms. Though seemingly isolated, their culture is common to all farms, as they have a tradition of having their children marry outside of the farm on which they grew up. In this way, the harvesters spread their knowledge about as well.
And though most denizens of the city see the harvesters as somehow rustic, this is entirely a preconception formed by meeting very few. They are, in fact, just as cosmopolitan and mixed up in the affairs of the city as are the other citizens.
Abbreviated EBCO, this organization certifies that the many oracles and prophets of the numerous religions of the Great City are what they say they are; individuals capable of telling people's fortunes and futures, or otherwise providing supernatural spiritual advice. How they go about making these certifications, when most oracles' pronouncements are (to say the least) obscure, is beyond most people to discern. But the board is an important player in city politics, feeling that it is important to prevent charlatans from threatening the livelihoods of their membership. This doesn't stop anyone from employing charlatans for oracular pronouncements and prophecy, but it does mean that a board certified oracle can charge a lot more than a charlatan (or other non-certified oracle) might.
A rather informal organization, the ratcatchers guild is, nevertheless, a cohesive association of not just rat-catchers per se, but also many other professions that deal with matters having to do with the depths of the Great City. It spans the city because their code is simple and effective: never take business from another member of the guild, and never allow anyone not a member to take business from the guild. Rumors that members of the guild are willing to kill to prevent non-members from doing their jobs are likely overstated, though not entirely implausible. Joining the guild is, again, informal, but essentially consists of an apprenticeship with a member for an arbitrarily long time. Often apprentices are kept as apprentices until the member dies, upon which time the full membership is passed on to the apprentice. In other cases (especially where the member can obtain a new apprentice to replace the old) apprentices are released into full membership earlier than the death of their mentors, but it's rare to serve less than a decade as an apprentice before being given full membership status.
Rats are a pervasive and pandemic problem of the Great City. Ratcatchers do not hope to have a chance of eradicating rats from any portion of it, and instead focus on just trying to keep areas they're contracted to deal with relatively rat free. Another common profession of guild-members is that of mortician for the lower classes. The rich may afford having the Architects build mausoleums for their dead. For most, however, disposal of a body is often a difficult affair. Some pay to have the body transported from the city to graveyards just outside the walls. But for those on the more interior parts of the city, the usual method of disposing of a body is to pay a mortician of the rat-catcher's guild to dispose of the body somewhere in the depths. Most don't ask where the bodies end up, and don't care, so long as they don't ever see the light of day again. There is a presumption that the bodies are handled with care and decorum, but there's often really no way to tell where a body is going once it's in the hands of the morticians.