City spacing

[nimling]

4 distance is pretty useful for ferrying garrisons from city to city, and fitting as many cities into your space as possible.
Really though, the best is to settle near sites with good stuff within 2 hexes, and at least one good thing in the central hex. Settling near Titanium is really buff for building up your cities. If that means settling 5-6 hexes away, so be it. Cities just need to get to pop 10 before trade routes, after that they can grow a bit further but there isn't much for it; nor is there an incentive to build a big capital, in fact usually my 2nd or 3rd city winds up bigger by endgame.
You might set aside a specialized super-city for production, in order to complete key wonders and projects asap, and that should have more tiles available to it; but it still won't get much past pop 22, due to the growth curve on cities.

Lots of small cities is better than a few big cities, especially with BE's flat-yield buildings early on - specifically laboratories. While you pay more in culture and research costs, the extra city will pay off research quite easily and culture isn't such a big deal once your health policies are sorted or alternatives for health are available.

 

[Evgenij]

I prefer to place my cities as close as possible - 3 tiles for ground cities, 2 tiles for water cities.

Pros:

1) City outproduces any other tile by far (simply by having so many buildings that you can build inside it). You should think of city as a sort of mega-tile-improvement. If you want to maximaze your production per tile - closest possible cities is the way to go.

2) Defending cities that are close is much easier. Sometimes, by attacking one of your cities, enemy will be in fire range of 1-3 other cities.

Cons:

1) You will get less strategic resources this way.