I have an Empire nestled in a far off corner of the world. It abutts the largest mountain range in the setting, cutting it off to one side. The next major humanoid popuplation is half a continent away on the other side. And since the setting is a giant cylinder, that makes them pretty isolated and self-contained. It sits between two great rivers, fed by snowmelt from the mountain range. And because of the distance between the two rivers, they exist in separate hemispheres and thus are in different seasons. So one of the two rivers is always in its seasonal flooding. The land between the rivers is at a slight downward incline, so the flooding feeds into seasonal rivers and streams that eventually feed into a massive lake, where the primary foodstuff of the empire grows along its banks. And since one of the rivers is always flooding, at least one side of the empire is in its flood plain and thus growing food.

The two rivers also are color code. The one to the west runs through an iron-rich desert, similar to the American southwest. When it floods, it picks up iron-rich clay making the river run ruddy red and the eastern bank (towards the empire) is rich in iron, silver, gold and other precious metals. The eastern river runs through marshlands and when it floods, the river overflows its banks and the entire area is one giant marsh. When this happens, the nutrient rich snowmelt causes algae blooms which are photo luminescent. So while its flooding, the marsh is constantly in a hazy blue glow giving it an ethereal and magical quality. Due to these algae blooms, the farmlands to the west (towards the empire) are especially fertile, so while farms exist on both sides, the eastern side is big on cash crops, like grapes (for wine) or pipeweed (tobacco).