Ancient bridges over the Loire in the Touraine area

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The ancient bridges over the Loire in the Touraine area were wooden structures erected during the Roman Empire to facilitate river navigation close to Fondettes and Tours, then known as Caesarodunum. Two bridges, constructed in the 1st century, appear to have been operational concurrently. The third bridge, erected in the early 4th century when walls enclosed the city, superseded the preceding two bridges, which were subsequently dismantled. The remnants of these bridges, unearthed around the turn of the 21st century, are discernible as lines of stakes embedded in the riverbed. They become visible during periods of low water levels, which are now occurring with greater frequency and duration.

The city of Caesarodunum, an open city established at the beginning of the era and intended to serve as the capital of the Turoni territory, was founded between the Loire and Cher rivers, in an area where several significant ancient routes intersected. Among these was a south-north road connecting Limonum (Poitiers) to Vindunum (Le Mans). This route is mentioned on the Tabula Peutingeriana and is believed to have followed a Gallic path, necessitating a crossing of the Loire. While the route of this road to the south and north of Tours is well-documented, its course through the alluvial plain is less well-known. However, it seems to have passed a few kilometers west of Tours. Until the early 21st century, the method used to cross the Loire—whether by bridge or ford—was unknown, as was the accurate point of crossing. Caesarodunum, established to the east of the Poitiers-Le Mans road, was linked to it by a branch road constructed to the south of Tours. However, the city, situated within the alluvial plain between the two rivers, also required specific crossing structures over the Cher and Loire rivers. Until the late 20th century, the precise nature of these crossings during antiquity remained uncertain, as acknowledged by Henri Galinié in 1985: "A bridge over the Loire, a river port, quays, and a landing stage are necessities that remain unlocalized." A similar question emerged in the early 4th century when the city appeared to have diminished in size and been confined to a fortified enclosure. The question of whether a bridge or ford crossed the Loire at that time—whether a new structure or a continued use of an older one—remained unresolved for some time.

In the late 20th century, and especially from the beginning of the 21st century, alterations in the Loire's hydrological regime (baseflow, more pronounced low-water periods) permitted the undertaking of new observations within the riverbed. These findings led to the discovery of three ancient bridges that had crossed the Loire in the suburbs downstream from Tours (the "Fondettes" bridge) or within the city itself (the "Île Saint-Jacques" bridge and the "Île Aucard" bridge).

In the 1970s, clusters of stakes in the Loire riverbed downstream from Tours were observed. To confirm the hypothesis of an ancient bridge crossing at this location and to date its construction, samples of stakes were subjected to analysis using carbon-14 dating and dendrochronology. It seems probable that this bridge allowed the Poitiers-Le Mans road to cross the Loire. The presence of a valley provided convenient access to the northern hillside, which was protected by a nearby oppidum. This structure possibly replaced an older one at the same location. The bridge was constructed entirely of wood and was erected in the early years of the common era. It was equipped with a wooden caisson at its northern end, which facilitated the transition between the bridge deck and the roadway. The differing structures of some piers suggest that one or more repair campaigns were undertaken, a hypothesis supported by the dating results for the stakes, which indicate a date of around 125 AD. Pieces of the bridge deck found near the northern bank suggest that the bridge was deliberately dismantled. In 1987, constructing a channel for a windsurfing competition destroyed the majority of these remains, leaving only a few stakes situated near the northern bank.

Adapted from Wikipedia (CC BY-SA). Photography via Wikimedia Commons.