Amiens develops from a simple place designating a 'the bridge over the Somme' to the biggest city in Gaul Belgium. Two key elements determine the fate of Amiens: the crux of the road network and its military role. The proximity of Britain and the Germania make Caesar hibernate at this place, Samarobriva, and roads Agrippa pass this point. Just establishing the road network, Amiens, accompanied by the regional and long-distance trade, grows rapidly and leads to its summit in the 2nd century. From the 3rd century, the crisis began, and the surface of the city is reduced and confined within the surrounding wall(castrum). But the city does not lose its military face yet, because the rostrum controls a road junction and a garrison is settled in the rostrum. With the road network built in Roman Empire, the castrum make up the base of the Middle Ages Christianization revives the city and attracts people around the Episcopal Church, built 'in the wall(intramuros)' in the 6th century. The process of urbanization is so slow that the surface within the wall is not filled until the eleventh century. Considering that the walls in the Middle Ages, called the Wall of Philippe Auguste, is based on Roman rostrum, it is assumed that there is a direct affiliation between two city, ancient and medieval. And the location of Amiens is always important throughout history, both ancient and medieval. But medieval Amiens is more the centre of the surrounding region than the strategic point of the road networks, Via Agrippa, and more the commercial city than the roman military city (civitas). And the thick dust, covered the archaeological site, shows the difference between the two cities.
Amiens se developpe d'un simple lieu-dit designant 'le pont sur la Somme' a la plus grande ville dans la Gaule Belgique. Deux elements essentiels fixent le destin d'Amiens: le noeud du reseau routier et son role militaire. La proximite de la Bretagne et de la Germanie fait hiberner Cesar a ce lieu, Samarobriva, et passer le reseau routier d'Agrippa. A peine s'acheve le reseau routier, la ville, accompagnee du commerce non seulement regional mais aussi lointain, croit rapidement et aboutit a son sommet au Ⅱ<SUP>e</SUP> siecle. A partir du Ⅲ<SUP>e</SUP> siecle, la crise commence, et la ville se reduite et s'enferme dans le castrum. Mais la ville maintient son visage militaire encore, parce que le castrum controle un noeud routier et une garnison s'installe. Avec les voies construites au Haut-Empire, le castrum constitue une partie de la base du Moyen Age. Christianisation fait ranimer la ville et attirer les ames autour l'eglise episcopale, elevee a l'interieur de l'enceinte(intramuros) au Ⅵ<SUP>e</SUP> siecle. Le processus de l'urbanisation, tres lente, fait remplir intramuros, jusqu'au XI<SUP>e</SUP> siecle. Considerant que les murs au Moyen Age, dit de Philippe Auguste, est fondes sur le castrum romain, on suppose qu'il y a une filiation directe entre deux ville, antique et medievale. Et la geographie strategique d'Amiens s'opere tout au long de l'histoire, tant antique que medievale. Mais Amiens medievale est plus le centre de la region alentour que le nœud de la reseaux routiers, Via Agrippa, et plus la ville commercial que la cite(civitas) militaire. Et l'epaisseur de poussiere couverte sur le site archeologique n'est pas negligeable