In my writing posts, I'm doing a series on worldbuilding. Previously, I introduced the topic by talking about your story world being a place where things can happen. Now we need to look at the actual place and think about geography.
This isn't just about the maps at the front of a fantasy novel. It's about what those maps imply and what goes behind the maps. Although we call it "world" building, it may not be about a whole planet, but rather about the places that affect your story. This is where some knowledge of geography and historical geography can help. For one thing, there's usually a reason why people live in a particular place. You can look at a map and see groupings of towns and cities. This is especially obvious in older settlements. People tended to come to places where they had things they needed to survive. Water was especially key, for crop irrigation, as a source for food (fish), as a draw for wild game, and as a means for transportation. It's easier to get to and from a place near a river, and it's easier to bring in goods and send away materials for trade.
Settlements might also arise near some other natural resource, like a mine or quarry. In a fantasy world with magic, cities might be built along ley lines. While many settlements arise because of easier access, there might also be settlements built because a location is safe and easy to defend, like a mountain outpost.
There can be less natural reasons for a settlement. A city might arise around a religious shrine that's based on an event that happened in that location. Once transportation technology comes along, it can drive settlement. If you travel on a road that parallels railroad tracks (or former railroad tracks) that date to the age of steam trains, you'll probably find a town or some kind of settlement every seven miles, whether or not there's a natural reason for there to be a town there. That's because steam trains required service every fourteen miles, and they set up the stops so that every other one served trains going in opposite directions. That meant there was a railroad facility every seven miles, which meant that the people who worked there needed a place to live and access to services. Since the trains stopped there, it was a good place to put things like stores. Other people then settled there to serve the railroad people and travelers, as well as people like farmers who brought good there to ship elsewhere. Churches and other civic institutions were established. Some of these towns became self-sustaining and continue today, even though the trains no longer stop there. Some remain as just a cluster of houses or an old church because there was little to keep people there if there weren't trains stopping.
The reason for the settlement and the ability to access it will affect the way that society develops. A place that's easy to reach by long-distance travelers is probably going to be more culturally diverse than the secure mountain fortress. A place with good resources is going to be wealthier, but also may have to be more fortified because others will covet that wealth and try to take it by force.
So, in planning the corner of your world where your story takes place, why are people living there? Can people from other places get there easily? What do they bring with them? What would happen to that society if something changed? If the mine is played out or the trains stop running, would the society continue? Do people feel safe living there? Is the place under attack often? How does this place compare to its surroundings or the rest of the world? Has the society spread from the initial settlement?
You don't have to actually draw a map, but knowing why people live there is a good start to figuring out how your place works. If you're using a real setting, it might help to look at some of the history of that place to understand why it's there and how it developed. That will affect who lives there and why, which could have an impact on your story.