The Vexin is a frontier country, and it shows. The plateau between the Seine and the Oise was for centuries the border between the kingdom of France and the duchy of Normandy, and the river Epte, which flows along its western edge, marked the line. In 911, the Viking chief Rollo and the French king Charles the Simple agreed at Saint-Clair-sur-Epte to give Normandy to the Norsemen, and the Vexin was the buffer between them. The history gives the villages a particular character, with fortified churches and the remains of castles.
This ridge road, at about a hundred and twenty metres, runs along the crest of the plateau between Seraincourt, Vigny and Oinville-sur-Montcient, in the Vexin français regional park. The landscape is open and agricultural, with huge fields of wheat, barley and rapeseed, divided by lines of trees and low stone walls, and long views over the countryside. The soil is chalky and light-coloured, and the fields glow in the sun.
The riding is easy and open: long, gentle curves and straights, a surface that is generally smooth, and very little traffic. On a clear day, you can see for miles over the plateau, and the church spires of the villages mark the horizon. In spring the rapeseed paints the fields a startling yellow, in summer the wheat turns gold, and in autumn the ploughed land is a deep brown. The wind is the main factor: across the open plateau it can be strong, and a crosswind can push a loaded bike.
The small villages have an old church, a few stone houses and a bakery or a bar, and some have farm shops selling local produce, such as honey, cider, and cheese. Seraincourt and Oinville are quiet and unassuming, and give a good sense of rural life. The area is popular with cyclists at weekends, so be prepared to share the road.
Meulan-en-Yvelines, about nine kilometres away, is the nearest town with fuel and shops, and you should fill up there. The smell of the plateau in summer, dry grass and warm earth, is a pleasant companion, and the long evenings make it a good place to end the day.