Albert Barnes Commentary Numbers 21:20

"and from Bamoth to the valley that is in the field of Moab, to the top of Pisgah, which looketh down upon the desert." — Numbers 21:20 (ASV)

In the country of Moab - Rather, in the field of Moab: the upland pastures, or flat downs, intersected by the ravine of Wady Waleh.

Pisgah, which looks toward Jeshimon - Or, “toward the waste” . Pisgah was a ridge of the Abarim mountains, westward from Heshbon. From its summit, the Israelites gained their first view of the wastes of the Dead Sea and of the valley of the Jordan; and Moses ascended it again to view the land of promise before his death.

The interest attached to the spot, and the need for a convenient name for it, has often led Christians to designate it as “Nebo,” rather than as “the mountain of, or near to, Nebo.” However, the latter is more correct: Nebo denoted the town (Isaiah 15:2; Jeremiah 48:1, 22) on the western slope of the ridge.