As early as 1934 Charlotte Perriand began to reflect on the architectural aspects of leisure activities for all, but it was with Les Arcs, her greatest work, that she completed her reflection on the art of living in the mountains. Alongside the developer Roger Godino, Charlotte Perriand displayed all the facets of her immense talent: design, urban planning, but also bioclimatic architecture, of which she was a pioneer. She had to deal with financial and time constraints in order to design most of the Arc 1600 and 1800. Thanks to her perseverance and growing inventiveness, her integration of architecture into the sites, her innovative and human approach to traffic, and the life she breathes into the resort, especially on the rooftops, she has made it a friendly place, in harmony with the environment. Thus, she designs the interior architecture of more than 4,500 homes, 25,000 beds, for an annual flow of more than one million people. Her wish to combine the art of living in the mountains with housing for the greatest number of people has been largely realised. AUTHOR: Jacques Barsac is the director of about 40 documentaries on art and history, including Charlotte Perriand, Le Corbusier, and Jean Cocteau. He has received the silver medal for publications from the Academy of Architecture and the trophy of the promotion of the architecture of the ministry of the Equipment for the film Le Corbusier. He met Charlotte Perriand in 1981 and accompanied her in the writing of her auto-biographical book Une vie de creation, published by Editions Odile Jacob in 1998. Since 2002, he has devoted his activity to the work of Charlotte Perriand. He is also curator of numerous exhibitions including The New World of Charlotte Perriand at the Fondation Vuitton (2019). 500 colour, 100 b/w illustrations