Specialize a Town
As you acquire more towns and build them up, you’ll be able to “Specialize” them once they reach a certain population. Specializing a town means it places an emphasis on one certain trait, such as food production. However, one of the specializations you can select is called “Hub Town,” and this allows you to earn a passive +2 Influence on the town for every settlement it’s connected to.
So, for example, if you have a central town that’s connected to two other settlements in your empire, Hub Town allows you to earn +4 total Influence every turn on that town. A town is considered “connected” if the borders of it meet another one of your settlements. While Hub Town isn’t meant for all your settlements, it can certainly be helpful for some of them.