Corumbia
Corumbia is a kingdom neighboring Samandra that was conquered by the Sultan.
First named in The Yellow Knight of Oz, ch. 5
Did you not, five hundred years ago, by a magic unrevealed to your illustrious advisors, conquer the neighboring Kingdoms of Corabia and Corumbia?
Where this is
placed In Oz worked out
read out of the chapters cited on this page, not stated in any one sentence of them
Same reasoning as Corabia — a conquered neighbor of Samandra, which is explicitly 'in the wonderful Kingdom of Oz.'