How close should cities be built in Civ 5?
In Civ 4, it was easy to figure out how close to build cities to maximize my territory, because the number of tiles they could use were very limited. In Civ 5, cities can use many more tiles (more than they'll need until they're huge), so I'm wondering how close I should build my cities. Is building the maximum number of cities even a good strategy in Civ 5 (as it was in previous Civs), or should I build a few giant ones far apart?
Probably related to this question:
You can't build a city in a 4hex radius of another city. It's useful to know this, because later you might want to build another city nearby and find out you can't.
It isn't as simple anymore. There's a number of things to think about
Initially your cities will only be able to access the tiles next to them. It will take a long time before your cities are generating enough culture on their own to add many tiles, unlike earlier civs where it was quite easy to boost to a full 2 square radius. So if you need a particular resource, you should either build next to it or be prepared to buy access to the tile.
Once a tile has been claimed, you can't "steal" it like in Civ 4 (except using the Great Artist in the base game, or Great General in the G&K expansion). So you want to make sure you establish your borders quickly before another Civ or city-state grabs those tiles.
Building additional cities causes increased unhappiness across your empire, and it also makes it more expensive to adopt social policies. So while spamming cities early will help you establish a large territory, it will penalize you in other ways.
So while the technical answer is that you maximize your potential territory without gaps or overlap by leaving 6 hexes between cities (since the maximum radius for a city is 3 hexes), I think you will find that blindly following that will be a sub-optimal strategy.
This is one of the systems in Civ 5 that is not necessarily more complicated, but certainly seems to be more strategic than it was in earlier civs.
This is a nice overview of the pros and cons of city count and size, but doesn't actually answer the question of how close together it makes sense to build them
@Mag, I don't think the question has a single answer. It's like asking what social policy tree I should use. The "right" answer is going to depend on what civ you're using, what the situation is with your neighbors, and your play style. But I edited to give the technical answer.
Just a comment - cities may expand the empire's borders for up to **5 hexes** away, though they can indeed only allocate citizens on a radius of 3 hexes.