So I am doing a write-up on the kingdom of Faland, and I need to know if anyone knows a term for a certain type of geographical formation. The map of the kingdom is here: http://www.farlandworld.com/farkingdom.htm
The light green area from the Ruin of Gemulla in the north to the Far City in the East Ladona in the south to Naxos in the west is the area I'm talking about. Its a large, relatively flat extremely fertile area that slopes gently down from the foothills of the Great Mts. to the Straights of Gor. What is the name of this type of land formation? Right now I am calling it a large, shallow basin, but that doesn't seem right.