The Royal Saltworks (Saline Royale) at Arc et Senans, built in 1779 by Claude Nicolas Ledoux, was a factory for the production of salt by heat evaporation of salted water.
The complex consists of 11 buildings, not only workshops but also workers home, and is laid out in a semicircle around the Directors House.
It was part of a bigger, unrealised plan of a circle containing the factory as well as other buildings of the ideal city of Chaux.
The factory was in production until 1895.