Here is the basis I have created after returning home from a double surgery. I am not able to work as fast as I wish, but here is the basis.
The ring of mountains I am building around the deep cleft river are the remnants of an ancient volcano. A later earthquake cracked and split the ring to allow the river to pass through.
Hopefully, I'll get more work done, but since still in recovery (docs say two months considering me age), I may not get much more done in the coming weeks. However, I will try.
Thanks for any and all C&C.