My purpose is a little different. The guys I play with are masters of verisimilitude and the unintended (by me) consequence. They are totally the guys who would say, "So, where is the Super Soldier formula kept and how can I get some? Because we need more vigilantes," or, "I think the roots of criminal behaviour are in poverty and despair, so I'm going to devote half an hour a day to turning dirt into gold, so I can raise the general income level. I'll need a secret way to trickle the gold into the population, though..."
So basically, in any post labelled Cities, I'll be talking about what I've discovered about cities so you can create more realistic cities. I make no guarantee about the accuracy of what I've discovered...it will generally be okay, but it might fall into the lacunae that the self-taught often have, and if I succumb to believing some nonsense that is out of date or shown to be wrong, let me know. Some wrong ideas still make useful campaign fodder.
I'm talking about cities, here. I'm not talking about hideouts, supersecret government locales, or mystic headquarters. Those have different forces acting on them.
So Where Is It?Your city has to be close to some kind of transportation, which makes sense: a city is a conglomeration of people who make their living by trading rather than by producing resources, such as farming or mining. If your city pre-dates the beginning of the twentieth century, then it's near water. (For drinking purposes, all cities end up being near water, because people need to drink...though I can think of workarounds. But I mean water that can be used as transportation to other places.) Near for pre-twentieth century means "within about 150 km of the ocean."
For cities that became cities after the start of the twentieth century, different forms of transportation are available. Horses, cars, and trucks are practicable at the beginning of the century, and air transport becomes possible by the middle of the century. Cities can be farther away, so long as they have access to a transportation hub or hubs.
Most big cities in North America are by rivers or bodies of water. There was a thriving transportation industry that carried materials up and down the Mississippi, and other waterways, too. (Heck, there were steamships that went up and down the river near my Canadian city.)
The later the city was founded, the further away the suburbs or towns, because people could travel farther, faster. When feet where the primary means of transportation, towns tended to be about fifteen kilometers apart...ten miles...because five miles was about as far as you could walk in the morning, do your shopping, and then walk home before dark. Obviously, as the city swallowed up small towns, it got bigger, but those towns are often neighbourhoods in the resulting city...a way for you to inject a bit of local colour into the area where the heroes live. ("This area? This was Mechaniton, where the only mechanic for forty miles lived!")
Where The Rich Folk Live (Generally Speaking)There's a wealthy area, and it's on an edge of the city towards the prevailing winds, whatever they are. (Usually in North America, they're west blowing east, but local geography can change that. Living on the water is usually more expensive...but not always!) Wealthy people generally don't want to live downwind of the factories and such; poor people don't have that kind of choice. They live where they have to.
Of course, as the city gets older and expands more, something might be built on the other side of the wealthy area...so it becomes less desirable, and there's a slow migration of the wealthy to a new area.