Designing a huge capital city for a custom world/custom campaign can be hard, Infact it is usually really hard, but having spent as much time as i have thinking about things to make the city cool... well its pretty cool.
Lets jump right into it.
Excuse my grammar and spelling, i wrote this down quickly before work
The City and surrounding area was dubbed Minar Lor During a long and prosperous era in the civilizations history (I mean the civilized world, by this point in recorded history most of the world has been documented/mapped if not already thoroughly explored as well as inhabited by populations aware of the rest of the worlds populations/locations).
An absolute Towering Behemoth, the city limits extend well into the range of 7000 km*2 on land with a large inlet bordering the northeast, and a population scraping 15million; Divided into four sections, laid out like a circle.
The inner city is reserved for the upper crust, High lords and ladies and the three great houses of Minar Lor. House Weinon, the lords of wealth, keepers of the treasury, and reagent to the artisans, merchants and craftspeople. House Batain, The house of justice, Generals, captains of the guard and defenders of the people; And house lacius, The thinkers and scholars, Politics, science and scripture. The inner city is mostly off limits to anyone save members of the great houses and a select few other members of society deemed worthy. The Middle city is the home of wealthy and well off merchants, scientists, wizards and craftsmen. Anyone can own a house in the middle city, but demand is high and coin among the common folk is usually not enough. The outer city is the home of the peasantry, Fishermen and mundane craftsmen, as well as the bulk of the cities standard guardsmen. The 4th tier isnt necessarily part of the city, Its known as the far city and extends outside the walls of the city and consists mostly of simple farm folk and their farms built close to the walls of Minar Lor.
Or atleast, thats what the city was like about... 8700 years ago, but alot changes when you subject an entire nations population to stasis for 6 1/2 centuries and subject the planet to a massive cataclysm that completely reshapes its entire surface.
Let me elaborate
The High Lords, Arch Wizards and Scientists of Minar Lor forsaw the coming of Shaa, The great comet. Shaa was on a trajectory that would graze the side of Naer, not crashing directly into it but definitely hitting it. In order to protect the massive population that resided in Minar Lor they created, in secret; expansive underground catacombs (Above the sewer system) that house thousands of chambers (need to find a name for "Stasis Pods" that sounds fantasy'ish) where the citizens of Minar Lor would be kept safe until the comet had passed. Unfortunately for them, after the population was tucked away in stasis (Working names for all this sciency/magical Hoo-Ha) the comet hit with more force than previously thought, causing massive earthquakes, clouds of poisonous dust/chemicals and a rain of fire that swept across the planet; the machines stopped working properly. Roughly a fifth of all the population of Minar Lor was killed outright when tunnels collapsed. Racks of chemicals that were to keep much of the people alive cracked and shattered, leaving many to starve to death in their long sleep. Damages to the controls and major systems were severe, this resulted in the automatic awakening system to malfunction, a few citizens awoke from their sleep only to be thrust into a world of destruction and death, watching haplessly as their friends and loved ones slept ignorant or died in their cages.