Referred to as the Colapis by Strabo (IV, 6.10, 207; VII, 5.2, 314) and Pliny the Elder (NH 3.28), the Kupa River belongs to the Danube hydrographical basin. Its length of 297 km makes it the third longest river in Croatia, although the longest one whose both spring and confluence are located within the country. Due to the strategic importance of its position on the far south-western edge of the Pannonian valley, on the crossroad of communications between Italy and the Balkans and between the Danube and the Adriatic, this river represents an interesting, although little studied, fluvial landscape with great archaeological potential.This paper is a preliminary assessment of an on-going PhD research project commenced in 2017 by one of the authors, Anton Divić. The project is focused on the reconstruction of the fluvial landscape of the Kupa River during the antiquity through the study of submerged and terrestrial archaeological sites, hydrographical and geomorphological data, historical sources, as well as through the analysis of ethnographical documentation on fluvial navigation. The focus of this paper, however, will be placed mostly on archaeological sources. This PhD project forms part of two long-term research programs carried by the two co-authors of this paper. The first one, dedicated to the documentation and protection of underwater cultural heritage in the inland waters of the Republic of Croatia, has been carried out in the last ten years by Krunoslav Zubčić. The second program, focused on the study of a well-preserved Roman river barge found at Kamensko next to Karlovac (Zubčić 2009; 2013), is a joint project between the Croatian Conservation Institute and the Centre Camille Jullian, a research laboratory of the Aix Marseille University and the French Centre for National Scientific Research (CNRS). The project, carried out between 2015 and 2018 under the co-direction of K. Zubčić and Giulia Boetto (Boetto 2016b), has been realised under the auspices of the Croatian Ministry of Culture and the French Ministry of Europe and Foreign Affairs. It allowed numerous data to be gathered on the ship structure, its cargo, and sailing programme, making Kamensko the first fluvial shipwreck in Croatia to be systematically excavated underwater.