Joshua 8:11

And all the people, even the people of war that were with him, went up, and drew nigh, and came before the city, and pitched on the north side of Ai: now there was a valley between them and Ai.

All the people. [The Septuagint translation gives a different and somewhat ambiguous idea of the mode of attack-Greek: kai pas ho laos ho polemistees met' autou anebeesan, kai poreuomenoi eelthon ezenantias tees poleoos apo anatoloon, kai ta henedra tees poleoos apo thalassees-And all the mentor war that were with him went up, and in their march came before the city on the east, and the ambush before the city from the sea (on the west).]

There was a valley (literally the valley) between them and Ai.