Joshua set up twelve stones in the midst of the Jordan, in the place where the feet of the priests who bore the ark of the covenant stood: and they are there to this day.
Some scholars have squirmed and quibbled over the setting up of two memorials, as mentioned here, declaiming on the stupidity of setting up a memorial where nobody would see it at the bottom of the Jordan, and other choice bits of human cavil.  Well, we thank God for the discernment of one like Pink, who has this: