Culture and Cities
Understanding the effects of culture on your civilization as a whole isn’t difficult. You gain points, you fill up your culture pool, and once full you gain a social policy. Easy as pie!
You may not realize, however, that culture also influences cities. The game does not telegraph this information as well as the information about your civilization-wide culture. If you open up a city’s details screen, however, you’ll see that there is a purple culture icon that is being filled just like the green food icon.
When this purple culture icon is filled your city will automatically grab another nearby tile. This means that cities with a lot of culture will rapidly expand their influence over an area.
The effects of this on your overall strategy are subtle. Cultured cities, because they grab land more quickly, can be built further apart. If your civilization is going after a conquest victory, for example, you may be restricted to building your cities very close to resources even if the tiles near the resource you need are less than ideal for city growth. If you intend to build a lot of culture improvements, however, you can choose a more ideal location a tile or two further away because your city will quickly gobble up surrounding land.
Culture cities will also expand your borders quickly, which can be useful if you’re in close quarters with another empire. Keep this in mind when thinking about planting a new city close to another civilization, and remember that other civilizations can’t encroach on territory under your culture influence unless you enter an Open Borders treaty.