Terrain is "the physical features of a tract of land." In Civilization IV, each tile has one base terrain type, may or may not have hills, and may also have one or more terrain features. Together, these are the tile's terrain, and they are assumed to cover it uniformly. Terrain has a strong effect on the movement and combat of land units.
Features of water are also called terrain for our purposes, even though the English parallel to "terrain" would be "marine." Terrain also affects naval combat, although it is far less complex there.
There are five base land terrain types. All require 1 movement point to enter, and all gain 1 bonus commerce if next to a river.
Improvements take 25% longer to build
Improvements take 50% longer to build
Rivers are exceptional terrain in that they are not "in" or "on" a tile, but they run between tiles. A river is considered adjacent to all tiles that it runs along, including all four tiles which touch a place where the river bends or empties into water. Rivers supply fresh water to all adjacent tiles. A river adds +1 commerce to all adjacent land tiles, unless they also contain an unimproved forest or jungle. Only cities adjacent to rivers may build Levees.
Hills are a sort of terrain feature, but they are not removable and thus in their own class. When a land tile has no hill, and is not a peak, it is flatland. See the Hill page for a bit more detail.
Terrain features are considered removable by Civilization IV. Many can be removed by Workers, but all features are removed when you build a city. Thus, if you build a city on a floodplain, the floodplain is removed and only desert is left.
Note that when scrubbing (clearing) fallout from a tile, any surviving improvements and/or terrain features on that tile will be also removed, though some of the former may then be rebuilt afterwards. You will not be able to rebuild an improvement that requires a particular terrain feature that has been removed by the cleanup (or else already destroyed in the nuclear attack), e.g a Lumbermill or Forest Preserve that had been placed on a now lost Forest.
A lake is any body of water smaller than a particular size in tiles, which is moddable but normally 9 tiles. Even though all water tiles benefit from Lighthouses, being adjacent to a lake is not sufficient for a city to be coastal.
Ice is a feature of water, although unlike land features it cannot be removed.
|Civilization IV |
|Warlords • Beyond the Sword • Colonization†|
|† Total conversion remake of the game Sid Meier's Colonization using Civilization IV engine|