Civilization 4: Terrain Improvements

Standard Improvements		Requires	Yield			Special
	Road All Land	The Wheel	-	-	-	1 move per 2 squares movement cost +1 square per move with Engineering Can cross rivers with Construction Connects trade network
	Railroad All Land	Railroad	-	-	-	1 move per 10 squares movement cost Connects trade network +1 Hammer to Mine, Lumbermill
	Cottage Grassland, Plains, Floodplains Tundra next to Freshwater Grassland Hills	Pottery	0	0	+1	Becomes Hamlet in 10 turns
	Hamlet Grown from Cottage	Pottery	0	0	+2	Becomes Village in 20 turns Cannot be built directly
	Village Grown from Hamlet	Pottery	0	0	+3	+1 Commerce with Printing Press Becomes Town in 40 turns Cannot be built directly
	Town Grown from Village	Pottery	0	0	+4	+1 Hammer with Universal Sufferage +1 Commerce with Printing Press +2 Commerce with Free Speech Cannot be built directly
	Windmill Hills	Machinery	+1	0	+1	+1 Hammer with Replaceable Parts +1 Commerce with Electricity
	Watermill Next to rivers	Machinery	0	+1	0	+1 Food with State Property +1 Hammer with Replaceable Parts +2 Commerce with Electricity Only one side of river can be used
	Lumber Mill Forest	Replaceable Parts	0	+1	0	+1 Commerce next to river +1 Hammer with Railroad Does not destroy forest
	Workshop Grassland, Plains, Floodplains Tundra next to Freshwater	Metal Casting	-1	+1	0	+1 Food with State Property +1 Hammer with Guilds +1 Hammer with Chemistry
	Farm Grassland, Plains, Floodplains Tundra next to Freshwater	Agriculture	0	0	0	+1 Food with Irrigation +1 Food with Biology Carries Irrigation with Civil Service
	Mine Hills	Mining	0	+2	0	Small Chance to Discover Resource +1 Hammer with Railraod
	Fort All Land	Mathematics	0	0	0	+25% Tile Defense

Resource Improvements		Resources	Yield			Special
	Farm Agriculture	Corn	+2	0	0	+1 Food with Irrigation +1 Food with Biology Carries Irrigation with Civil Service
		Wheat	+2	0	0
		Rice	+1	0	0
	Mine Mining	Copper	0	+3	0	+1 Hammer with Railroad
		Iron	0	+3	0
		Coal	0	+3	0
		Uranium	0	0	+3
		Aluminum	0	+3	+1
		Gems	0	+1	+5
		Gold	0	+1	+6
		Silver	0	+1	+4
	Camp Hunting	Deer	+2	0	0
		Fur	0	0	+3
		Ivory	0	+1	+1
	Plantation Calendar	Bananas	+2	0	0
		Dyes	0	0	+4
		Incense	0	0	+5
		Silk	0	0	+3
		Spices	+1	0	+2
		Sugar	+1	0	+1
	Quarry Masonry	Marble	0	+1	+2
		Stone	0	+2	0
	Pasture Animal Husbandry	Horse	0	+2	+1
		Cow	+1	+2	0
		Pig	+3	0	0
		Sheep	+2	0	+1
	Winery Monarchy	Wine	+1	0	+2
	Fishing Boats Fishing	Clam	+2	0	0
		Crab	+2	0	0
		Fish	+3	0	0
	Whaling Boats Optics	Whales	0	+1	+2
	Well Combustion	Oil	0	+2	+1
	Offshore Platform Plastics	Oil	0	+2	+1
	Tribal Village (non-player controlled)	-	-	-	-	Bonus for discovering

The yield given in these tables are the amount of Food, Hammers and Commerce the improvement gives in addition to the base (unimproved) value of the terrain the improvement is built upon. All resources also give a fixed bonus of 1 food, 1 hammer or 1 commerce to the base value of the terrain, in addition to the improvement bonus. This bonus is given even if you do not improve them, or build a different improvement than the standard one on them.

For standard improvements the terrain types it can be built upon are listed below the name. Resource improvements can always be built on their respective resources, regardless of terrain. For them, the required technology is listed below the name instead.

Farms and Mines are both standard improvements and resource improvements. The latter function overrules the former. So if you build them on one of their associated resources their effect is given in the second table, not the first.