UPDATE (September 9, 2014, 2:45 PM Pacific Time)
Shortly after publishing this blog, I came across a forum post that contradicts the information presented in this blog post. As such, I will review the actual source code in the Civilization V dll, do some more testing with the game, and revise the post as necessary. In the meantime, I'll leave the unaltered post here, for posterity. I apologize for the inconvenience.
A lot of buildings in Civilization V mention that they are affected by tiles or resources "near the city", but this quality of being "near a city" is poorly-defined within the game. So what exactly does it mean? I haven't seen any in-depth articles about this topic on the web or in the game's Civilopedia, so I thought I'd outline the important bits here.
Basically, a tile is "near" a city if that city was the first city in its respective empire to claim that tile within its workable radius.
So if you have a single tile or resource that lies between two cities, and both cities' workable ranges overlap that same tile, then that tile is not "near" both cities. It is only "near" the first city that owned that tile. This means that if you go into the city management screen and assign the second city to work that tile, it may receive yield bonuses associated with any improvements or buildings that affect it (such as the stable buffing pasture resources), but the tile's contents will not be considered "near" that second city for other purposes. This includes:
- requirement of an improved Horse or Ivory to build a Circus,
- requirement of an improved Horse, Cow, or Sheep to build a Stable,
- requirement of an improved Iron to build a Forge,
- requirement of an improved Stone or Marble to build a Stone Works,
- requirement of an improved Gold or Silver to build a Mint,
- wonder production bonus from nearby Marble,
- requirement that the city be adjacent to a Mountain in order to build an Observatory,
- trade route income from resource diversity,
- and so on...
Examples of "near the city"
Improved Resource for Building Requirement: Which city can build a Circus?
Say you have two cities (for example Rome and Antium) whose workable ranges overlap a pastured Horse. Rome was the first city to claim the Horse tile. Rome can, therefore, build a Circus (assuming Trapping has been researched). If you go to the management screen of Antium, you can assign it to work the Horse tile (which prevents Rome from being able to work that tile), but Antium still cannot build a Circus. That is, two cities cannot build a building that requires they both have the same tile.
[LEFT] Rome has annexed a tile containing horses and is building a Circus.
[RIGHT] Later, that tile overlaps with Antium's workable radius, but it cannot build a Circus because the horse was originally claimed by Rome.
Alternatively, if a resource is claimed by a city's culture, but is outside of a city's workable radius (four tiles or more away), then it never counts as "near" that city. But if you found a second city that does contain that tile within its workable radius, then the resource will count as "near" the city!
Improved Marble: Which city receives the wonder-production bonus?
This is also how Marble's wonder bonus works. The wonder-production bonus is only given to the first city to claim the tile containing Marble within its workable radius. If a second city overlaps that tile, it does not receive the wonder-production bonus, even if it is currently working the tile.
Antium has Marble within its workable radius, but it does not get a production bonus towards the wonder because the Marble tile was first claimed by Rome.
The wonder-production bonus only applies to Rome, regardless of which city is working the tile.
Trade Route Income: Which city owns the resource for "resource diversity"?
"Resource diversity" for trade routes is also subject to this same rule of "nearness". The original city to claim the tile gets credit for that resource in trade route resource diversity. Having another city overlap on that resource does not grant resource diversity to both cities.
Antium is working the horses and marble, but they do not count towards the trade route diversity because the tiles are "near" Rome.
When settling a "trading" city, keep this in mind. If there are tiles that overlap the 3-tile radii of two cities, you may want to purchase luxuries or strategic resource tiles in the city you wish to have as a trading hub to ensure the resources go to it. This is especially true if you are playing Portugal, since you get double gold for resource diversity (1 Gold instead of 0.5 Gold for each unique, mutually-exclusive resource between the two cities).
When to purchase tiles?
Because of the way resources/tiles are "near" one city, there are some cases where you may wish to purchase tile(s) to a guarantee ownership to a certain city. Relying on the normal cultural expansion is not recommended.
Some examples of these cases include:
- Two cities' workable radii overlap a Stone. City A is on Plains and therefore would not be able to build a Stone Works even if it owned an improved Stone. City B is on Grasslands, so you may wish to purchase the Stone tile in this city so that it can build a Stone Works for the extra production and happiness.
- There are Horse/Iron tile(s) within range of two cities. One city will become your unit-factory city (i.e. city with Heroic Epic), and the other will not. Purchase at least one Horse/Iron tile in the unit-factory city so that it may build a Stable/Forge to speed the production of your military units.
- In general, if two cities are within range of any same resource tile, you may to wish direct which city gets ownership for trade route resource diversity purposes, or for distributing clustered resources.
Maximizing clustered resources
In an area where a single resource is clustered, you should be careful of which city claims the tile(s) first. If a single city is first to claim multiple copies of a single resource, then other nearby cities whose workable range overlaps with that resource will not be able to benefit from having that luxury "near" the city.
2 copies of stone lie between Thebes and Memphis.
If Thebes buys one stone tile, and Memphis buys the other stone tile, then both cities can build a Stone Works!
If one city already has the resource, but there is another tile with the same resource, you can purchase that tile in the city that does not have it--that way both cities would own a copy of the resource "near" the city. By carefully planning which city annexes which resource tile and preventing one single city from annexing all tiles containing clustered resources, you can ensure that multiple cities will meet the requirements for constructing buildings like the forge, stable, stone works, or circus.
Memphis can now build Stone Works as well!
"Worked by the city" tile buffs do not care which city is "near" the tile
For other buildings that simply buff tiles or resources "worked by the city", the "near" the city rule doesn't apply. Any city that met the requirement(s) to build such a building, and does build the building, will receive the bonus from working the relevant tile(s) regardless of whether the tile or resource is "near" the city. Such buildings include:
- bonus food on Wheat, Deer, and Bananas from Granary,
- bonus production on Marble and Stone from Stone Works,
- bonus production on pastures from Stable,
- bonus food and production on sea resources from Lighthouse,
- bonus gold on Gold and Silver from Mint,
- bonus science on jungles from University,
- bonus production and gold on sea resources from Seaport,
- bonus production on tiles adjacent to rivers from Hydro Plant,
- bonus Gold on Stone and Marble from the Mausoleum of Halicarnassus wonder,
- bonus food and production on desert from Petra wonder
The difference between "nearness" and "ownership"
Further complicating the rules is the additional concept of tile ownership. Which city "owns" a tile, is independent of--but similar to-- which tile is "near" the city. Just like with "nearness", cities "own" tiles if that city is the first to claim the tile (or purchase it).
In this case, however, that ownership does not care whether the claimed tile is within the city's workable radius! A city may expand its borders up to 5 tiles away from natural cultural border expansion, even though its citizens can only work within 3 tiles. If the city is captured, traded away, or razed, all of its owned tiles will switch ownership (or become unclaimed in the case of razing).
a new city in owned territory gives the new city ownership of its adjacent tiles,
but not the other tiles that are "near" the city.
Shown here, the new city
Zaragoza will be assigned the Aluminum as being "near" it, since it is within 3 tiles.
Zaragoza does not "own" the Aluminium though, since it was acquired by Madrid in Madrid's 4th ring.
This will come into play when new cities are founded near existing cities that have strong culture, and which have already claimed or annexed tiles in the vicinity of the new city. Those already-claimed tiles still count as "owned" by the original city. However, if those tiles are outside of the old city's workable radius (4th or 5th ring tiles), but inside the workable radius of the new city (within 3 tiles), then those tiles will be considered to be "near" the new city.
If the old city is captured, traded away, or razed, then its owned tiles will transition to the new ownership (or become neutral in the case of razing), even if they are "near" the new city. Likewise, if the new city is captured or traded away, the tiles originally owned by the old city but are "near" the new city will not transfer with the new city. They will stay with the old city.
[LEFT] Zaragoza gets credit for the nearby Aluminum for resource diversity, even though Madrid owns it.
[RIGHT] If Zaragoza is traded away or conquered, it only keeps its adjacent tiles.
Tiles adjacent to a city (the innermost ring) are an exception. They are always considered to be both "owned" by and "near" the adjacent city. The only exception is if the adjacent tiles are stolen via a Citadel.
Unique buildings follow the same rules
Civilizations' unique buildings also follow the same rules outlined above. There's only a few unique buildings that are relevant to this mechanic, so I'll discuss them below:
The Polish Ducal Stable
The Polish unique building is a stable replacement. It follows the same rules outlined above. It requires that the city have at least one pasture improvement nearby. So if two cities share the same Horse, Cow, or Sheep within their workable radius, and they do not have access to any other nearby Horse, Cow, or Sheep, then only the first city to claim that tile will be able to build the Ducal Stable (once the resource is improved).
The bonus gold and production on pastures that is provided by the Ducal Stable does not care if the worked tile is "near" the city. If you met the requirement to build the Ducal Stable in a city, then that city will receive the bonus yield on any pasture resource that it works. As a quick reminder, the bonus yield provided by the Ducal Stable is given to the underlying resource, and not to the pasture improvement (the pasture improvement is only required to build the Stable; once built, even animal tiles that are not yet improved receive the bonus yield).
The Arabian Bazaar
Arabia's unique building is a little bit more complicated, since it has a unique mechanic associated with it.
The Bazaar provides an extra copy of any improved luxury resource that is near the city.
Example of a luxury being overlapped by two cities. It doesn't matter which city works the luxury tile.
As long as the Bazaar is in the first city to have claimed the resource, you get the duplicate.
Say Mecca in the above example a source of Incense in its outer ring of workable tiles. Mecca can build a Bazaar and gain two extra Incense for Arabia to trade away. Say that Medina's workable radius overlaps with the Incense, but Medina does not have a Bazaar. You can use the city management screen to assign Medina to work the Incense. In this case, even though Medina is working the Incense, and Mecca is not, and Medina does not have a Bazaar, you will still receive a duplicate Incense because it is still "near" Mecca (which does have a Bazaar).
The effect of this is that if you found a new city that can overlap with luxuries of an existing city with a Bazaar, you can assign that new city to work those luxuries without losing access to the duplicate source of the luxury! You can safely trade away your excess luxuries even while still in a period of expansion without worrying about the trade deal becoming broken if you shuffle around worked tiles between cities.
The bonus yield on Oases and Oil is not affected by the "near" the city rule, as this is a simple tile buff. If the city currently working the Oasis or Oil has a Bazaar, the tile will receive the bonus yield, regardless of whether that city is the tile's original owner.
Unique buildings that buff tiles "worked by the city" do not care about "nearness"
Unique buildings that buff tiles "worked by the city" follow the same rules as regular buildings that use the "worked by the city" rules. These include:
The Aztec Floating Garden simply buffs any lake tile worked by that city, regardless of the lake's original owner.
The Iroquois Longhouse simply buffs any forest tile worked by that city, regardless of the forest's original owner.
The Siamese Wat follows the same rules as the regular University. It simply buffs any jungle tile worked by that city, regardless of the tile's original owner.
I hope these clarifications are helpful to you fellow Civ-players. Just so that it doesn't seem completely irrelevant, I would assume that these same rules will apply to resources in the upcoming Beyond Earth, since it is based on the same engine. However, I do not know for certain.