lost_civantares said:As far as I can tell the closest city of yours gets it, the only qualification is that is has to be in your borders.
Not even that, you can chop forests in unclaimed land for shields, although there's probably a penalty. What's fun is when your culture pushes your borders beyond the usable radius of any of your cities and you can chop forests that are within the radius (but not yet the cultural borders due to your superior culture) of another civ's city.