The ANR ‘FRONTIER’ project, which starts in 2024, focuses on imperial borderlands between the 5th century BCE and the 5th century CE. In the context of Central Asia, which combines the steppe and the oasis world, the territorial cohesion of the great empires is based on a policy of intense and multi-scalar expansion, as well as on the emergence of large exchange networks. Nevertheless, the centre-periphery approach only partially accounts for the notion of frontier – here understood as a zone of contact with or without a specified boundary line – namely its manifestation, perception and permeability, culturally and materially as well as geographically. This project thus proposes to address this issue by focusing not on the centre, but on the borderlands of Central Asian empires from Sogdiana and Bactria to Northwest China and the ‘Hanging Passages’ of the Upper Indus valleys. The focus put both by the written sources and field investigations on the cores of empires has considerably slowed our knowledge of marginal areas: in those, the imperial expansion strategies and its manifestations remain largely unexplored. A main part of the ‘FRONTIER’ project is to gather unique datasets based on fieldwork data so as to identify mobility patterns along circulation routes. In order to tackle this problematics, two 4-weeks archaeological survey campaigns were scheduled in the Spring of 2024: the first one in Uzbekistan in the Zeravshan valley to complete the documentation of the remarkable and previously unknown rock art material (petroglyphs), the preliminary study of which attests to its links with other areas of Central Asia as well as the Upper Indus region from the Bronze Age onwards; the second one in Tajikistan in the Karategin (Rasht) valley, a hitherto poorly known area which yet served as a major circulation passageway between Central Asia and Northwest China via the Kyzylart Pass (4 280 m). These survey campaigns aim at recording and quantifying the available documentation, completed by data from the existing archaeological bibliography and a partly-inventoried corpus of petroglyphs. Our presentation will address the ‘FRONTIER’ project as a whole and present the latest results of the conducted surveys.