What was the significance of the great heap of stones?
Joshua 8:29 (ESV)
29And he hanged the king of Ai on a tree until evening. And at sunset Joshua commanded, and they took his body down from the treeand threw it at the entrance of the gate of the city and raised over it a great heap of stones, which stands there to this day.
Rock piles were used throughout the conquest in order to commemorate significant events. Here, the rock piles symbolize what happens to kings who set themselves against God’s people: they are destroyed.
29 And he hanged the king of Ai on a tree until evening. And at sunset Joshua commanded, and they took his body down from the tree and threw it at the entrance of the gate of the city and raised over it a great heap of stones, which stands there to this day.