On every continent and for tens of thousands of years, men have traced signs on rock faces. We now know that they did so not only in caves but also – and perhaps above all – in the open air. This episode takes us to discover this art that is called “rock art” in the majestic site of Piedra Furada, in the Brazilian desert. Alongside Paul Bahn and Jean-Loïc Le Quellec, two of the best international specialists in rock art, we set off to discover exceptional yet largely unknown works, meeting experts, enthusiasts and local populations.