In the sandstone chaos south of Paris, between Nemours and Rambouillet, more than 2,000 engraved shelters, usually cramped, were discovered. Some were reported as early as the 19th century and most of the discoveries took place in the late 20th century thanks to the tireless surveys of the “Groupe d'Étude de Recherches et de Sauvegarde de l'Art Rupestre” (GERSAR). There is at least one Paleolithic engraving, whose formal characteristics are similar to those of Lascaux, and there are above all, in addition to explicitly protohistoric or historical age designs, thousands of geometric engravings, mostly dominated by grid patterns and deep grooves arranged in parallel series. Various arguments suggest that a substantial portion of these abstract engravings go back to the VIIIe millennium BCE, i.e. the end of the first Mesolithic. In 2017, new research began with the support of the French Ministry of Culture: the main objectives consist in archiving several shelters by documentation including 3D modelling while new means of relative dating are investigated. At the same time, an ambitious outreach program is underway to ensure that everyone — especially inhabitants living in the vicinity — becomes a protector of this very fragile prehistoric heritage, sometimes in the midst of highly touristic areas.