Pont "Saint-Michel" et ponts sur le Cosson dits "chastrés" ou "chartrains" (également sur communes de Saint-Gervais-la-Forêt et Vineuil)
MonumentHidden Treasure
Pont "Saint-Michel" et ponts sur le Cosson dits "chastrés" ou "chartrains" (également sur communes de Saint-Gervais-la-Forêt et Vineuil), located in Blois (Loir-et-Cher), is a medieval landmark built in the Middle Ages. The monument is currently closed to visitors.
Key facts
- Type
- autre
- Period
- Medieval (11th-15th century)
- Location
- Blois, Loir-et-Cher, Centre-Val de Loire
- Visit
- Closed to visitors
- GPS
- 47.5826, 1.3492
- Mérimée Reference
- PA41000037
Fascinating medieval remains in the heart of the Loire Valley, the Saint-Michel and Chastrés bridges have spanned the Cosson since the 13th century, bearing unique witness to forgotten hydraulic engineering.
© Wikimedia Commons
History
In the heart of the Loire Valley, between the towns of Blois, Saint-Gervais-la-Forêt and Vineuil, a group of medieval bridges stretches across the Cosson like a well-kept secret of French heritage. The Saint-Michel bridges and the Chastrés bridges - also known as "Chartrains" - together form one of the last tangible reminders of how travellers once crossed the wide, flooded Loire valley in medieval times. These engineering structures, listed as Historic Monuments in 2006, embody a memory of the road infrastructure of ancient France that few regions have managed to preserve. What makes this ensemble truly exceptional is its unique morphology: it is not a bridge in the traditional sense of the term, but a system of long dikes interspersed with arches and spans designed to let the currents of the Cosson through. This technique, inherited from Roman traditions and perfected in the Middle Ages, made it possible to cross not just a river, but an entire alluvial plain prone to flooding. The medieval traveller thus travelled on an elevated causeway, progressing from bridge to bridge across an ever-changing aquatic landscape. The Saint-Michel bridges, whose medieval pier bases are still visible, mark out an ancient Roman road that linked Blois to its southern surroundings. Their silhouette, fragmented in the riverbank vegetation, now offers walkers and history buffs an open-air archaeological experience, far removed from the tourist crowds that flock to the Château de Blois. The Chastrés bridges, meanwhile, are still partially passable, offering an authentic crossing of the Cosson on modern-day arches that have taken over from the vanished medieval structures. The natural setting enhances the heritage experience: the Cosson, a small forest river with slow, wooded waters, flows through a wild landscape of wet meadows and riparian forests. Photographers, naturalists and history buffs all come here to marvel at structures that the centuries have barely touched. The visit, free and silent, invites you to take a melancholy stroll along these dykes where time seems suspended between two floods.
Architecture
The most remarkable architectural feature of this complex is its embankment design: rather than a single bridge spanning a channel, the medieval builders opted for a system of long earth and masonry embankments, interspersed with arches to allow the secondary arms and flood zones of the Cosson to drain away. This approach, inherited from Roman traditions of building roads on raised pavements, demonstrates a perfect understanding of the hydrological behaviour of the river and its alluvial plain. The materials used correspond to local resources: limestone from the Blois region, widely available in the subsoil of the Loire Valley, used for the piers, arches and dyke facings. The medieval arches - of which a few bases remain for the Saint-Michel bridges - probably have semicircular or slightly broken profiles, characteristic of Romanesque and Gothic architecture. The arches of the Chastrés bridges, rebuilt in the modern era, have flatter shapes, reflecting technical developments in the 16th and 17th centuries. The bridge stretches over several hundred metres and crosses several communes - Blois, Saint-Gervais-la-Forêt and Vineuil - making it an unusually large infrastructure structure for the medieval period. This territorial dimension, which involved the cooperation of several riverside seigneuries in the maintenance and management of the crossings, is in itself a remarkable feature of the medieval organisation of the region.
Related Figures
Comtes de Blois (XIIe-XIIIe siècle) — seigneurs territoriaux probablement à l'origine de la construction et de l'entretien des ponts Saint-MichelThibaut V de Blois — comte de Blois sous le règne duquel les ponts Saint-Michel sont mentionnés pour la première fois en 1202Louis Ier de Bourbon-Vendôme — seigneur influent de la région au XIVe siècle, contemporain de la première mention des ponts Chastrés en 1343Ingénieurs des Ponts et Chaussées du XIXe siècle — responsables de la création de la nouvelle chaussée qui entraîna l'abandon des anciens ouvrages médiévauxInspecteurs des Monuments Historiques (2006) — artisans de la reconnaissance patrimoniale et de l'inscription protectrice de l'ensemble
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Frequently Asked Questions
Where is Pont "Saint-Michel" et ponts sur le Cosson dits "chastrés" ou "chartrains" (également sur communes de Saint-Gervais-la-Forêt et Vineuil) located?
Pont "Saint-Michel" et ponts sur le Cosson dits "chastrés" ou "chartrains" (également sur communes de Saint-Gervais-la-Forêt et Vineuil) is located in Blois, Loir-et-Cher department, Centre-Val de Loire region, France.
When was Pont "Saint-Michel" et ponts sur le Cosson dits "chastrés" ou "chartrains" (également sur communes de Saint-Gervais-la-Forêt et Vineuil) built?
Pont "Saint-Michel" et ponts sur le Cosson dits "chastrés" ou "chartrains" (également sur communes de Saint-Gervais-la-Forêt et Vineuil) dates back to a period built in the Middle Ages (11th-15th century).
Is Pont "Saint-Michel" et ponts sur le Cosson dits "chastrés" ou "chartrains" (également sur communes de Saint-Gervais-la-Forêt et Vineuil) open to visitors?
Pont "Saint-Michel" et ponts sur le Cosson dits "chastrés" ou "chartrains" (également sur communes de Saint-Gervais-la-Forêt et Vineuil) is currently closed to visitors.