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Origin and history

Arc-et-Senans' royal saline, built between 1775 and 1779 during the reign of Louis XV, is a former salt production plant designed by architect Claude-Nicolas Ledoux. Located near the forest of Chaux, it was intended to transform the brine extracted from the salines of Salins-les-Bains, transported by a 21 km saum pipeline. This ambitious project aimed to modernize the production of salt, which was then essential for the conservation of food and subject to the gabelle, a royal tax.

The choice of site was motivated by its proximity to the forest of Chaux (wood source for heating), the plain of La Loue, and an altitude allowing the gravitational transport of the brine. Ledoux first imagined a monumental project in the form of a square, rejected for its cost and excessive symbolism. The final plan, in a half circle of 370 meters in diameter, included workshops, worker housing, and a central management house, reflecting a utopian vision of an autarchic industrial city.

Construction began in 1775, with a first stone laid on April 15, and the operation began in 1779. Saumoduct, a major technical innovation, consisted of trunks of eviscerated fir ("turneaux"), gradually replaced by cast iron in the 19th century. Despite leaks estimated at 30%, 135,000 litres of brine were delivered daily. The grade building, 496 metres long, concentrated the brine by evaporation prior to processing in the "darks", where it was heated in stoves for 48 hours.

Saline, although designed to produce 60,000 quintals of salt annually, never reached this yield, with a maximum of 4,000 tons per year. After the liberalization of the salt market in 1840, it was auctioned in 1843. Its decline accelerated with sea salt competition and well pollution, resulting in its closure in 1895. Classified as a Historic Monument in 1926 and restored from 1930, it was listed as a UNESCO World Heritage Site in 1982.

Ledoux's architecture, marked by doric columns, frontons and rigorous symmetry, blended industrial functionality and symbolism. The director's house, with its integrated chapel, dominated the whole, while the workers' houses (berniers) and workshops (maréchalerie, coopererie) formed a harmonious half circle. Ledoux's initial project, an ideal city in a complete circle, later inspired landscape developments to symbolically complete this utopia.

Today, saline houses a museum dedicated to Ledoux, temporary exhibitions, and a cultural centre. It also hosts events such as the Festival des Jardins et des master-classes musicales. Its partially preserved Saumoduct and restored buildings demonstrate its pioneering role in the industry and architecture of the Enlightenment.

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