The exhibit concluded here, where we were invited to move a stone from one basin to the other, in honor of the cairn found on Robben Island, which we'll be visiting later. In a 1995 reunion of Robben Island ex-prisoners, Mandela spontaneously put down a stone in the middle of the quarry. Each former prisoner followed suit, forming a cairn that we'll see in our later visit. But today we were invited to be part of that history by adding our stone to the pile.