to Strabo (Geographica, IV, 1, 11). Orosius noted that Gaius Marius, who was sent by Rome to stop the Cimbri and the Teutons, had established his camp not far from the confluence of the Rhône and the Isère. The excavations on the upper part of the plateau of Lautagne ( south of the centre of Valence) revealed the presence of devices of a defensive nature dating from the 1st century BC: Thus the foundation of the city could have come from a Roman military camp. Even under the Roman domination, the Allobroges tribe established themselves north of Isère, and repeatedly rebelled against the Roman occupation. The was the last to take place, identifiable with the modern commune of Soyons (Solo by Livy, Epitome 103) in 62 BC. The selection of the site The city of Valentia was established on a terrace on the left bank of the Rhône river, south of the confluence of the Isère and from the Drôme. This geographical situation is understood by the crossing of several routes of transport and communications: Valentia had a privileged place in north-south trade through the Rhône and at the Via Agrippa. Valentia was part of east-west routes since the different paths, which traversed the plain from the Isère Valley and the Drôme (), converged on the city. The Rhône was crossed at Valence on a ferry, by ford or over a bridge. The ancient city The city of Valence, as many Gallo-Roman cities, received an orthonormal plan. The orientation of the urban streets network successively followed cadastres "A" inclined N, 12°30'E and "B", inclined N, 23°E, in the Valence plain. We know the decumanus of the city thanks to the discovery of a pavement and a sewer a few metres north of the city hall. The cardo of the urban network was the Via Agrippa that crossed the city in a straight line from the southern gate of the city to the old gate and Tower of Aion, north of the city, which later became "Tourdeon" (now destroyed). It was along the Via Agrippa that a forum was located, probably surrounded by a , curia, a temple, etc., of which the location is unknown. To the south of the presumed forum site, between the Rue du Théâtre and Rue Vernoux the ruins of the thermae were discovered. This thermal water supply, and more generally that of the city of Valentia,