Basins are areas that are delineated via topography and define an area in which water flows downward toward a common point. Basins are also referred to as “watersheds” and “catchments.” They are a unique feature type that is often shown on natural resources related maps. As with all features, the basin features might be the main focus of the map or just supporting information. When you have created new basins with your GIS and are displaying them in map form for the first time, you need to give them credibility by displaying them with topography as the background layer in the form of a hillshade dataset. With the basin boundaries laid on top of the hillshade, the viewer will immediately see how the basin boundaries line up with the ridges on the hillshade. Additionally, regardless of whether your basins are the central feature of the map, you usually want to include a hydrography layer with the basins. Because basins are tightly coupled conceptually with streams and rivers, your audience will be keen to see them in relation to your basins. (See Figure 6.90 for color suggestions.)