|Gold||+1 (vanilla and G&K only)|
|Movement cost||All remaining points|
|Possible resources found||None|
Terrain feature found everywhere across the world. Unlike other features, it doesn't occupy a separate terrain tile, but extends between several tiles. A river usually starts next to a mountain tile, and it always ends in a larger water tile, such as a lake or ocean. A river will also turn adjacent flat desert tiles into flood plains, adjacent snow tiles to tundra tiles, and adjacent tundra tiles to plains.
Some buildings are only available when the city is built next to a river (or a lake). They are:
Rivers are the most important source of fresh water, simply because they are more common than lakes, and border a bigger number of tiles. The benefits of fresh water are many: Farms may be built on adjacent hills and tundra tiles (something not possible without fresh water); furthermore, these Farms receive an additional +1 Food early on (with the Civil Service technology), while all other Farms have to wait until the Industrial Era. A number of special buildings may only be constructed in a city if it has fresh water access. Also, the Hydro Plant building can only be built in a city on a river, which adds +1 Production to all tiles next to the river! All this means that constructing cities next to rivers is very advisable.
Rivers may turn also into a strategic advantage, or a hindrance for you. Units expend all of their movement points when crossing rivers - even if the tiles are connected by roads - until the civilization learns the Engineering technology, and they receive a -20% penalty when attacking units on the other side of a river. So, if you control the banks of a river, you may gain a very important advantage over an enemy.
As of Brave New World, rivers no longer provide additional Gold yield for neighboring tiles. However, there's an additional Gold bonus when opening International trade routes to cities built on rivers.
Traditionally, cities have been built along rivers, and for good reason. Rivers provide a steady source of water, both for drinking and irrigation, improving the farmland around the city. They also protect a city, as it is quite difficult to mount an assault against a city across a river. Furthermore, rivers are a source of additional food, and the larger ones may be used for transportation, which is incredibly important for trade (since the energy needed to transport cargo along a river is only a fraction of that needed for land transport). Historically cities such as Frankfurt and Paris have thrived exactly because they turn into local trade hubs.