From Ornans we rode on to Salins-les -Bains, an ancient town set between these two prominent cliffs. M. Vauban has been at work here too, as once the product of the town was a matter of national significance.
The limestone of the region contains layers of geological strata, including the remains of a prehistoric sea. In medieval times this was mined as salt. Water was pumped down into the salt layer and extracted as saline. Boiling off the water caused the salt to crystallize, and a relatively pure form could be made in this way. Salt was obviously a key commodity in preserving meat, as well as in seasoning food. They called it "White Gold."
This is a view of the town from the Belvedere up at one of the forts. We were surprised to find it less steep than it looked. At one time this fort was used as a holiday camp for children, but it is now run as chambres d'hote - or a bed and breakfast. The views must be spectacular.
We learned a lot about the processes involved in salt extraction, and also about the "Gabelle", or salt tax which was a major cause of discontent in Pre-Revolutionary France.
At the time when the salt-works were in operation the whole place must have been black with smoke from the constantly burning fires used to heat the saline - a major industrial centre. You might imagine that it is a peaceful backwater now -- but you would be wrong.
All day a constant stream of traffic roars through Salins-les Bains. Riders of very powerful motorbikes seem to enjoy revving up as they go through. Perhaps they are testing their brakes on the white-knuckle hairpin bends locally. Tourists seem to be the twenty-first century version of white gold.