🗺️ Border Expansion

4 spread rules138 improvements spread14 boards

Borders in Old World are entirely deterministic, unlike in other games.

Legend your territory another player's 1 tile acquisition order resource pull urban pull adjacent water gap fill Minor City starting tile a buyable tile

Summary

Tile acquisition is entirely deterministic in Old World, unlike other games. The page below sets out the rules the game uses to expand your borders, whether the expansion comes from a Border Boost card, from urban expansion, or from buying tiles with the Colonies law or in a Landowner Seat.

Tiles

A City's Territory is made up of its surrounding Tiles within the City's border. Most Improvements can only be built within a City's Territory. City Territory is expanded by building Urban Improvements, training Specialists near City borders, or when you Buy Tiles. Water tiles within a City's territory allow Water Transport.

In-game concept text, Territory

You gain a tile whenever it meets one of the rules below. Then, the rules run again to see if you gain any other tiles because of the new tile you just gained.

Tile acquisition rules

Claimable land is any tile that is not Mountain, Volcano, Water. The game goes down this list, considering all your owned tiles.

Resource pull. Your borders expand to a tile with a resource when it neighbors one of your tiles that has no resource.
Urban pull. Your borders expand to an urban tile when you own a tile next to it.
Adjacent water. Your borders expand to a water tile when you own two claimable land tiles that sit next to each other and both touch that water tile. Mountain and volcano tiles work the same way. When the water tile has only one possible adjacent land tile and you own it, your borders expand as well.
Gap fill. You gain a tile when you already own the tiles on both sides of it.

Your borders expand to the horses only, because one resource tile cannot pull another resource tile.

You gain everything next to the urban tiles, because an urban tile pulls the borders around it.

Red owns a tile on both sides of the empty tile, so red gains it.

You own both sides of this tile, and it goes to the lower left city, because the game assigns tiles in the priority order SE, SW, W. The lower left city owns the tile to the SW of this one, so it gets the tile.

Adjacent water

Taking the highlighted land tile first also gives you the central water tile, because the only claimable tile next to it is a land tile you own. The other two tiles then chain off that one.

Taking the highlighted land tile gives you one tile only, because you have no other tile along the coast. You get that tile because you own land on two sides of it.

You get the water tile because you own one of the two land tiles beside it, and it does not matter that the other one is unowned.

You do not get the water tile when one side is an enemy tile, because you do not own it. An enemy tile acts the same as an unowned tile.

Mountains and volcanoes follow the same rules as water.

Chains

You can 'chain' border expansion.

Adding a specialist on the farm ends up adding 7 tiles.

First you take every tile next to the specialist, which are the three tiles labeled 0.
The game tile has a resource and sits next to a tile you now own that has none, so resource pull takes it. The fish works the same way.
The game takes the water tile to its east, because that is the only land boundary of that water, marked tile 2.
The last water tile now lies between that tile and land you already owned, so gap fill takes it.

Founding

Founding works the same way, because it takes everything within 2 tiles of the Settler and then runs all the same rules.

You pick up the ore and the wheat, because they border tiles you own that have no resource.

You would make a minor city here, because you own every land tile bordering a city site.

City Sites without a Tribal Settlement can be turned into a Minor City if all of the Urban Tiles connected to the City Site are surrounded by your territory.

In-game help text for the Minor City

Minor Cities. If you surround all land tiles of a city site, you make a minor city. Minor cities are worth 2 VP, give +25 Money and cost 4 Food upkeep.

What can expand borders

Trigger	When	Range	Code
Found a city	Settler on a City Site	2 from the founding tile	`Game.createCityNext → Tile.getCityInitTiles`
Place a specialist	first specialist on a tile	1	`Tile.onSpecialistChange → spreadBorders`
Finish an urban improvement	any of the 133 urban improvements	1	`Tile.doImprovementFinished → isImprovementBorderSpread (bUrban)`
Finish a Spreads Borders improvement	Harbor, every Holy Site, every wonder	1	`isImprovementBorderSpread (bSpreadsBorders)`
Add urban	Worker action, Builder leaders only	1	`Unit.addUrban → spreadBorders (before makeUrban)`
Buy a tile	your unit on the tile	0	`Unit.buyTile → getExpansionTiles(0)`
Growth bonus	card, tech card or event	0 from each picked tile	`City.growBorders → findGrowBorderTile`

Building an urban improvement takes the tiles next to it, in the same way a specialist does, and it can chain in the same way as any other border expansion.

Buying tiles

Tiles can also be bought with a Unit adjacent to a City border when the Colonies law is active, or if the City is a Landowners Family Seat.

In-game concept text, Buy Tiles

You can buy tiles with the Colonies law or in a Landowners seat, under the conditions below.

You need a unit on the tile. It can be a military or civilian unit.
The tile cannot be urban.
If the tile is water, it must touch land. Being Coastal is not enough, it must touch land.
The tile needs to be adjacent to a tile you already own.
The same border expansion rules run on tile buying.
Cost: (base + per × (tile purchases for that city + tile purchases for any of your cities ÷ 2)) × (distance from the city + 1) ÷ 4, with a minimum of 1, rounding down at each step. Every purchase raises the count of tile purchases for that city and the count for any of your cities.

You can buy any of the dashed tiles for the price listed. Buying the hill will also grab the cattle because of border expansion rules.

Swapping tiles

You can also swap tiles between your own cities without Colonies or a Landowners seat. The tile cannot have an improvement on it, and moving it cannot split the other city's territory. Swapping costs the same as buying.
Swapping tiles between cities of the same family costs Money only.
Swapping tiles between cities of different families gives +20 opinion to the family gaining the tile for 20 turns, and −40 to the family losing it for 40 turns.

Cost by distance and purchases

Money	0 bought	1 bought	2 bought	3 bought	4 bought	5 bought	6 bought
distance 1	10	15	20	25	30	35	40
distance 2	15	22	30	37	45	52	60
distance 3	20	30	40	50	60	70	80
distance 4	25	37	50	62	75	87	100
distance 5	30	45	60	75	90	105	120

Training	0 bought	1 bought	2 bought	3 bought	4 bought	5 bought	6 bought
distance 1	5	7	10	12	15	17	20
distance 2	7	11	15	18	22	26	30
distance 3	10	15	20	25	30	35	40
distance 4	12	18	25	31	37	43	50
distance 5	15	22	30	37	45	52	60

Border Boost and similar events

Border Boost is the clearest example, and it takes 6 tiles. The game scores every possible tile, takes the highest scoring one, and chains from it, then repeats until it has taken all 6 tiles. You can end up with far more than 6 tiles, because you always get 6 tiles plus everything they chain to.

Score term	Value
seeded roll	1 to 100
terrain	Arid 300, Lush 500, Marsh 100, Temperate 400, Tundra 100
height	Hill 200
vegetation	Jungle 200, Jungle (Cut) 100, Trees 200, Trees (Cut) 100
river	100
passable	200
on the trade network	100
resource	1200 / 1600 / 2000 / 2400 (values below)
per neighbour	height Coast 10, Lake 20, Mountain 40, Volcano 40 (land candidates only); +10 if this city's; +20 if your team's (or taken this pick) and improved; otherwise its resource value ÷ 5
distance	× 3 ÷ (distance from the city + 2)

The event below takes +2 tiles. Each tile is labeled with its score.

The roll is random, but is seeded by the city tile and restarted each pick, so the tiles grabbed are always grabbed in the same order.

Source	Tiles
Bonus cards	Small 2, Average 4, Large 6, Huge 8
Tech card	Border Boost (Aristocracy): 6 to every city
Events	Age of Expansion 5 (×3), Annexation 5, Farming by the Stars 4, Land Grab 3, Gift of Land 4/8 (×2), Growth Opportunity 4, Proof of Friendship 2, Rebel Gladiators 4. Cave of Patriarchs carries -1, which does nothing: growth needs a positive value.

Resource border values. Horses 2400, Marble 2400, Ore 2400, Camels 2000, Crabs 2000, Dyes 2000, Elephants 2000, Fish 2000, Pearls 2000, Barley 1600, Cattle 1600, Fur 1600, Game 1600, Gems 1600, Pigs 1600, Salt 1600, Sheep 1600, Wheat 1600, Citrus 1200, Ebony 1200, Goats 1200, Gold 1200, Honey 1200, Incense 1200, Jade 1200, Lavender 1200, Olives 1200, Silk 1200, Silver 1200, Sorghum 1200, Spices 1200, Wine 1200. Resources without a value score 0 but are still pulled.

Losing tiles and gotchas

Tiles are never removed from a city. You can lose a city, but the tiles go with the city.
If City Razing is on, and a City is Razed, then the Tiles become unowned because the City no longer exists.
You can take a Tribal Site as a minor city even with units still on it, which turns the camp into a minor city immediately.

Every land tile around the city site is yours, so you take the site as a minor city and then take the tiles around it as if you had founded a city there, which reaches 2 tiles out.