Hi, I use the following set of rules created by Dreifel to keep the world looking as beautiful on turn 400 as turn 1.
Should be able to find the original post in the forum somewhere, worth a look as it covers far more... below is is an abridged version, taken from my mod.
#GCON_Dreifels'_Terrain_Rules
Dreifels' Terrain Rules
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^{Dreifels' Terrain Rules,} although the over all effects may appear subtle, in game play terms it means, {Irrigate} Grasslands and Flood Plains, {Plant} Forests on Plains. Hills and Mountains are to be {Mined,} Elven Forrest, Ancient Forrest tiles, build {Roads.}
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^The changes to the food/citizen ratio and the lowered relative food from Coasts Tiles, but with increased food bonus for Fish and Whales, with the changes in relation to other bonuses for resources with food, all add to the general increased to the 'food by citizen' factor.
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^When founding a Coastal City, look for a minimum of three {Sea} Tiles within their active range, as the {Costal} Tiles will not give enough food to grow the City.
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^{The above changes} along with the use of Thin Roads, on the Map, means the Map stays beautiful throughout the game, and is not swallowed by ugly mines everywhere!
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^{Thanks Dreifels'}
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^{Grassland, Cities yes} primary use as a food producer when Irrigated, Road allowed.
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^{Flood Plain, Cities yes} primary use Food production, at which they excel at when Irrigated, Road allowed.
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^{Plains, Cities yes} maybe Irrigated, but with diminishing returns, will not support a Cities population. The primary use is to be forested for shields as a medium Mine. Roads allowed.
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^{(continued)}
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#DESC_GCON_Dreifels'_Terrain_Rules
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^{Forrest, Cities Yes} Forrest Cities are allowed.
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^{Elven Forrest, Cities Yes} in practice this is really only of use to the Elven Races. Good tiles, build a Road to maximise production.
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^{Ancient Forrest, Cities No} Good tiles, build a Road to maximise production.
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^{Hills, Cities Yes} used for Mining, no Irrigation although a Road maybe built.
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^{Mountains, Cities Yes For Dwarven Races} No for everyone else, used for Mining, no Irrigation although a Road maybe built.
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^{Volcano, Cities No} can be Mined and a Road may be built to gain additional food, whether it will be worth it in the long run is another matter.
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^{ Desert, Cities No} Irrigation is not possible, but Roads are.
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^{Tundra, Cities No} not recommended for anything... although it maybe Irrigated to the same level as an Irrigated Plain if needed, again Trees are you best bet.
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^{Coast}, weak food production but better with a Resource, Harbour or port.
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^{Sea}, food production good but better with a Resource, Harbour or port.
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^{Ocean} food production good but better with a Resource, Harbour or port.
