|This article is about an older version of DF.|
In fortress mode, rivers can be seen as blue
~ tiles stretching from the top of the map to the bottom. A single fortress can have up to 2 rivers - one on the surface (depending on the biome), and one underground (guaranteed to exist).
The surface river, if your biome has one, is visible when you begin your game, running parallel to the cliff face and zig-zagging back and forth randomly. It is marked by numerous fords which allow it to be crossed; in order to cross it in any other location (particularly for caravan wagons), bridges must be built. Occasionally, the river will split and rejoin, creating small islands, or create a very wide pool. In most climates, the river (and any murky pools) will freeze up in the winter, although the length of this freeze is heavily dependant on geographical location; rivers in tropical areas may never freeze at all.