The "watchmaking metropolis", as La Chaux-de-Fonds is usually referred to, was added to the UNESCO World Heritage List on 27 June 2009, together with neighbouring Locle, because of the exceptional value of its urbanism and industrial architecture. It is no coincidence that it was precisely here in this watchmaking municipality that the only Art Nouveau movement in Switzerland arose, the so-called "Style Sapin". The land of watchmaking was a fertile one for progressive ideas, new currents of thought and the opening of art towards new horizons. Other factors contributing to the eruption of a modern trend were the wealth of its industry and the progressive nature of the people who ran it, the high level of education of its working classes and an opening out towards the world due to constant commercial exchange.
The small town of La Chaux-de-Fonds was totally destroyed by a fire in 1794 and over its ruins a new urban plan was designed that set the foundations of the industrial city that would prosper in the 19th century. It seemed that everything in the town had been designed to ensure watchmaking production efficiency. Contributing to this was the quality of its lighting, the rationalism of its transport routes, the pragmatism of its urban planning, the types of workers' housing and its production centres. For example, its Art School was founded in 1870 by master engravers who were concerned about the training of their workers. This was how the Style Sapin first took off under the leadership of the school's director, Charles L'Eplattenier. Students at the Art School were the main protagonists of the style, amongst which was the future Le Corbusier. They worked equally well on the designs and decorations of a villa for a master engraver (Villa Fallet) as they did for the look of watchcases, work that was collectively rewarded at the Milan International Exhibition in 1906. Everything in La Chaux-de-Fonds is indeed about watchmaking.