In 1775, Louis XV decided to build a new Saline in Franche-Comté to face the increase of the salt's demand and the wood's deplection around Salins-les-Bains.
The King chose its favorite architect, Claude-Nicolas Ledoux, to carry the project out. Ledoux found the place between the villages of Arc and Senans very interesting to build this new factory. First, it was a big plain space, which meant the chance to build huge buildings. Secondly, the villages were nearby the 22-thousands-hectares-long Chaux forest, offering all wood necessary to the evaporation. And last but not least, Arc and Senans were 104 meters lower than Salins. Since there was no salt or salty water on site, the drop would allow the salty water to flow from Salins to Arc-et-Senans. To do so, Ledoux decided to build a bold project : a "saumoduc", a 21 kilometers long wooden pipe.
The Royal Saline was built between 1775 and 1778. Ledoux designed in a smart way. On a rational level, it is in shape of a semi-circle to lessen the travels but also watch out the workers. On a symbolical level, it also echoes the sun's path into the sky.
This ambitious project have never been fully successful. Salins has never sent enough salty water to Arc-et-Senans: it kept the saltiest water for its own production. Plus, leaks and robbery made 10 to 30% of this water disappear on its way to Arc-et-Senans. These are the reasons why the Royal Saline has never been quite profitable, but also why it closed much sooner than the Great Saline, in 1895.
