Two Examples of Roman Fortification in the Western Alps: The Néron in the Isère and the Pic-de-Luc in the Drôme

Two elevated sites dating back from the late third and early fourth century can be compared along alpine passageways : one is the Neron overlooking Grenoble and the Isere valley, the other is the Pic-de-Luc overlooking the former capital of Luc-en-Diois and the Drome valley. Both actually share similar features : big water-tanks, different buildings and fortification with one tower at least. Both sites are also provided with access tracks on difficult ground. Their common features lead one to consider that these settlements were meant to control the main alpine roads for a military purpose. As some of these remains are common to other sites in the Isere valley and surmised in other areas of the higher Drome valley, the configuration of such connecting valleys urges one to raise the assumption that defence facilities had been built along the roads to the western alpine passes. This assumption is only a research-clue to be bolstered by fieldwork, yet it can be found relevant in the alpine historical context of the third and fourth century. Indeed, several previous events contribute to viewing the Alps as a new strategic target as of the late second century : when Clodius Albinus seceded, then at the time the Alamans raided the area in the mid third century. But, above all the “Gallic Empire” in the late third century and the appointment of a Prefect of the Guards in the Grenoble area may have made such a defence system useful in the Alps between Gaul and Italy, according to the imperial strategy.