Joshua set up the twelve stones that had been in the middle of the Jordan at the spot where the priests who carried the ark of the covenant had stood. And they are there to this day.
References for Joshua 4:9
Now the priests who carried the ark remained standing in the middle of the Jordan until everything the LORD had commanded Joshua was done by the people, just as Moses had directed Joshua. The people hurried over,
and as soon as all of them had crossed, the ark of the LORD and the priests came to the other side while the people watched.
The men of Reuben, Gad and the half-tribe of Manasseh crossed over, ready for battle, in front of the Israelites, as Moses had directed them.
References for Joshua 4:12
About forty thousand armed for battle crossed over before the LORD to the plains of Jericho for war.
References for Joshua 4:13
That day the LORD exalted Joshua in the sight of all Israel; and they stood in awe of him all the days of his life, just as they had stood in awe of Moses.
References for Joshua 4:14
Then the LORD said to Joshua,
“Command the priests carrying the ark of the covenant law to come up out of the Jordan.”
References for Joshua 4:16
So Joshua commanded the priests, “Come up out of the Jordan.”
And the priests came up out of the river carrying the ark of the covenant of the LORD. No sooner had they set their feet on the dry ground than the waters of the Jordan returned to their place and ran at flood stage as before.
References for Joshua 4:18
On the tenth day of the first month the people went up from the Jordan and camped at Gilgal on the eastern border of Jericho.
References for Joshua 4:19