The city of nantes developed at the confluence of the Erdre and the Loire, a strategic choice of location. The relationship between the city and the river therefore merits investigation, from the earliest agglomeration in Antiquity to Contemporary period. The aim of current research is to understand the evolution of the river around the city in order to identify any residual elements of earlier Loire landscapes, and to evaluate which sites would have been suitable for a river crossing prior to the 9th century AD, and for a port prior to the 13th century AD. It is now proved that upstream and around Nantes, the components of the Loire landscape at the scaleof the Loire Valley (alluvial plains, islands and channels) have evolved little, as geographic entities, from the end of Protohistory to the Modern period. Nevertheless, the network of channels that developed in the middle of the Medieval period transformed sites previously connected to land into islands. The line of medieveal bridges in Nantes was therefore based on a chain of islands that developed much earlier. This suggests that it replaced an ancient crossing probably related to the implantation on either side of the Loire the cities of Condevicnum (nantes) and Ratiuatum (Rezé). Arcaelogical observations have not yet confirmed this hypothesis. In the immediate vicinity of Nantes, research has revealed the complex relationship and permanent interactions between the city and the river over time. The physical link between them was materialized by a channel called "Canal Saint-Félix". New data has confirmed the artificial nature of this channel, which must therefore have been a canal. Its, either Medieval of Antique, remains uncertain, since repaeated dredging has eradicated the oldest traces. it is clear that the canal was built before the 13th century AD, as historical mentions, of the ports of Maillard and Pierre de France attests to its existence, and after the end of the Iron Age or at the beginning of Antiquity, for reasons of water-level compatibility between the canal and the river. More precise information about its creation is essential, as this link was vital to the city, for the transportation of goods and men, the transport of water necessary for the economy and for its defense, by acting as a moat at the foot of the city wall. Several periods in the history of the city can be considered as politically and economically favourable to the creation of such a singularly ambitious hydraulic structure. The canal was dug either during the creation of the agglomeration in the 1st century AD of our era during the installation of the castrum at the beginning of the 4th century AD. The canal may also have been developed under the leadership of bishop Felix in the 6th century AD, according to his contemporaries, as he undertook a great deal of hydraulic work on the river network around Nantes. Finally, the canal might have been built during the construction of Bouffay Castle, at the end of the 10th century AD. The line of bridges can still be seen in ancient documents but, in the 1930s, the canal was filled in. Recent archaelogical discoveries have identified a defensive bastion where the islet of Saulzaie lay, in the middle of the canal, at the end of the line of bridges crossing the Loire. Such transformations responded to evolutions in the economic and defensive needs of the city, which should be better understood after future excavation campaigns.