A long and flat stage took us past the twin saltworks of Salins-les-Bains and Arc-et-Senans, home to a long history of salt production.
The Jura region was underwater some 200 million years ago, and as those seas dried up, they left behind extensive deposits of salt. This salt dissolved in groundwater and bubbled to the surface in salt springs. Since at least the 8th century, the inhabitants of Salins-les-Bains starting collecting this brine and boiling it over an open fire using wood from the nearby forests.
By the 18th century, the salt content of that brine was starting to drop, and the forests arounds Salins-les-Bains were depleted, slowing the production of salt. The French monarchy was heavily dependent on salt production through the tax known as the gabelle, so the Ferme Générale, the king’s personal tax service, started investigating means of improving salt production. In 1771, King Louis XV appointed the architect Claude-Nicolas Ledoux the Inspector of Saltworks in Franche-Comté, and Ledoux set about designing his dream salt factory. The site chosen for the new Royal Saltworks was the town of Arc-et-Senans on the Loue River and, more importantly, south of the great Forest of Chaux that would provide a seemingly unlimited supply of wood for the burners. A 21 km pipeline would be built from Salins-les-Bains to carry the brine to the new factory.
Ledoux was not content with building any old saltworks. He was determined to make the Royal Saltworks the center of an Ideal City built to Enlightenment principles of order and rationality. In his plan, the saltworks occupy the center of a circle consisting of outbuildings for the factory workers while outside the circle lies the planned city. The factory was constructed by 1779 and started producing salt. However, the French Revolution in 1789 put a halt to Ledoux’s plans for the city.
The Royal Saltworks continued production until 1895, when rail travel made it easier to bring sea salt into the interior of the continent and evaporating brine was no longer worth the cost. The Salins-les-Bains managed to hang on until 1962, when it was shut down after nearly 1200 years. The two sites were inscribed on the UNESCO World Heritage list in 1982 and are open to the public today.