Rivers do not run in squares: instead they run along the edges of squares. Any square with a river along its edge produces one extra Image:Gold (Civ3).png Commerce if worked by citizen laborers within a city radius. Also, rivers are sources of fresh water, allowing irrigation of adjacent squares without Electricity. A city that is built adjacent to a river (or another source of fresh water) does not need an Aqueduct to support a population above 7 (but still has a maximum cap of 12).