Cities can use a [36 hex grid](https://gaming.stackexchange.com/questions/7887/is-there-a-limit-to-the-number-of-tiles-a-city-can-use-in-civ-5/7912#7912) at maximum.

It seems to me that 3 is also the maximum "range" at which one can purchase new tiles. Is this correct, or is it possible to buy land further off?