Albert Barnes Commentary Joshua 4:13

"about forty thousand ready armed for war passed over before Jehovah unto battle, to the plains of Jericho." — Joshua 4:13 (ASV)

The plains of Jericho, consisting of the higher terrace of the Jordan valley, are almost seven miles broad. The mountains of Judaea here recede somewhat from the river, and leave a level and fertile space, which, at the time of Joshua’s invasion, was principally occupied by a forest of palms. Hence, the name city of palms (Deuteronomy 34:3).