The Lignon du Forez comes out of the Monts du Forez with a cold, clean hurry, and by the time it reaches the plain around Boën it has cut itself a shallow gorge through old volcanic rock. This is the country west of Lyon and north of Saint-Étienne that most people cross on the autoroute without noticing, and that is exactly why it is pleasant. The Forez plain is a wide, flat bowl of pasture and orchards, and the mountains stand along its western edge like a wall with the road folded into the foot of it.
Sail is the one to remember: above the village a ruined medieval castle, Couzan, perches on a rock spur, and you can see it from the road long before you reach it. Boën is the practical neighbour, a small town with shops, a bakery or two and the usual fuel station, and it sits in the middle of the little Côtes du Forez wine area, a thin-skinned red country built on gamay. Saint-Germain-Laval, a bit further north, is a pleasant old market town. For anything larger, Montbrison is about twenty kilometres away and has everything.
The riding here is gentle rather than dramatic. Departmental roads run along the river and up into the hills with tight little bends, short climbs and a lot of blind crests where the hedges close in, so keep the speed honest. Surfaces are generally decent but patched, and farm traffic is the real hazard: tractors, loose gravel at field entrances, and mud after rain in the lower lanes. The best hours are early, when the mist lies on the plain and the hills above are already clear, and late in the day, when the light goes yellow on the stone farms.
The river is why this stop is marked for swimming. In summer the Lignon has pools below the bridges where locals wade in, but the water is mountain water, so it is bracing even in August, and levels change quickly after storms upstream. Pick a spot with a gravel bank, leave the leathers in the shade and give yourself time to warm up afterwards.
This is a fine place to start or end a day if you are heading for the Vanoise or the Jura, because you are on the quiet side of Lyon and the roads east are an easy morning's transfer away. Bring cash for the smaller villages, where the one bar may not take cards.