Aqueduc gallo-romain de Rosnarho
MonumentHidden Treasure
Aqueduc gallo-romain de Rosnarho, located in Crach (Département 56), is a historic monument. The monument is currently closed to visitors.
Key facts
- Type
- autre
- Location
- Crach, Département 56, Bretagne
- Visit
- Closed to visitors
- GPS
- 47.6389, -2.9727
- Mérimée Reference
- PA56000019
The only Gallo-Roman aqueduct bridge in Armorique, this line of masonry piers descending to the River Auray bears witness to the boldness of Roman hydraulic engineering in Brittany. A 440-metre vestige like no other in the Grand Ouest.
History
In the heart of the Rhuys peninsula, between the calm waters of the River Auray and the hedged farmland of the Morbihan, the Gallo-Roman aqueduct of Rosnarho emerges from the undergrowth like a fragment of eternity. Its ancient masonry piers, arranged in a regular line for around a hundred metres, are irresistibly reminiscent of the great aqueducts of southern France - but here, the silence of Brittany lends a very special intensity to the discovery. This is the only bridge-aqueduct from the Gallo-Roman era known to date in the whole of the Armorican region, making it an absolute exception in the archaeological panorama of the Grand Ouest. The singularity of this monument lies as much in what remains as in what has disappeared. Fifteen of the original twenty-five arches still stand, at heights of between 0.80 and 1.60 metres - enough to reveal the majesty of the original structure, but not enough to hide the ravages of time. The ramp marking the western end of the structure has also been preserved, giving the attentive visitor the chance to mentally reconstruct the complete layout of this monumental facility. Visiting Rosnarho also means passing through a landscape that has remained largely unchanged since ancient times. The site, discreetly signposted, requires a minimum of curiosity and effort - rewarded by a rare archaeological immersion, far removed from the tourist crowds that invade the nearby Carnac megaliths. Photography enthusiasts will find the low-angled morning or evening light a perfect blend of Roman stone and Breton vegetation. The Rosnarho aqueduct is part of an area of Morbihan that is exceptionally rich in heritage: just a few kilometres away, Locmariaquer boasts megalithic alignments and monumental dolmens, while the River Auray, a historic navigation route, has been shaping the human settlement of this land of water and moorland for thousands of years. A combined visit is a must if you want to embrace the long history of Brittany.
Architecture
The Rosnarho aqueduct illustrates Roman civil engineering techniques applied to the constraints of an Atlantic territory. The structure is made up of a line of masonry piers built of small rubble blocks bonded with tuileau mortar - a hydraulic mortar made from bricks and crushed roof tiles, typical of Roman buildings exposed to damp. This technique, perfectly suited to the conditions in Brittany, partly explains the partial survival of these structures over almost two millennia. The original twenty-five arches were spaced 2.50 metres apart, a regular rhythm that bears witness to a rigorous modular design. The current height of the fifteen preserved arches varies from 0.80 to 1.60 metres, a variation that reflects both the hazards of conservation and the adaptation of the structure to the natural topography descending towards the River Auray. The river section, which has now entirely disappeared, consisted of eleven arches on twelve piers set in the riverbed itself - a technical feat that required careful foundations in an unstable alluvial substrate. The aqueduct carried water through a masonry pipe running along the top of the piers and arches, protected by a waterproof coating. The ramp preserved at the western end of the structure bears witness to the care taken to manage the hydraulic gradient, a sine qua non for the system to function properly by gravity. Although modest in size compared with the great Mediterranean aqueducts, Rosnarho represents an undeniable technical feat for a northern province of the Empire.
Related Figures
Christophe-Paul de Robien — magistrat et érudit breton, premier à signaler et décrire les ruines vers 1750Gustave de Closmadeuc — archéologue vannetais du XIXe siècle, auteur de la première étude scientifique approfondieJules César — dont la conquête de la Gaule (52 av. J.-C.) amorça la romanisation qui rendit l'aqueduc possibleLes Vénètes — peuple gaulois d'Armorique, habitants de la région à l'époque de la construction
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Frequently Asked Questions
Where is Aqueduc gallo-romain de Rosnarho located?
Aqueduc gallo-romain de Rosnarho is located in Crach, Département 56 department, Bretagne region, France.
Is Aqueduc gallo-romain de Rosnarho open to visitors?
Aqueduc gallo-romain de Rosnarho is currently closed to visitors.