Joshua set at Gilgal the twelve stones they had taken out of Jordan. They put it there so that they could tell their children what had happened to the parents in the past. Jordan river was having a flood. But as soon as the priests, who carried the ark, stepped into the waters, the upstream stopped flowing and they were able to cross the river via dry land. God asked them to carry 12 stones from the middle of Jordan where priests with the ark had stood.
God wanted this to be remembered all through the ages so that every generation knows how God had carried their forefathers all through the difficulties of their life like an eagle that carries its little ones.
“Like an eagle that stirs up its nest and hovers over its young, that spread its wings to catch them and carries them on its pinions” Deuteronomy 32:11