The Danubian provinces of the Later Roman Empire (the area between present day eastern Bavaria and the Romanian Dobruja) are not well known, due to the paucity of literary sources from or about that region. Yet it was regularly at the centre of the great political, military and religious events of Late Antiquity, when the fate of the Empire was played out in the context of the great invasions/migrations. Located on a critical point of the Empire's borders, these provinces had an important network of fortifications, around which was organised the Romanisation of the territory. Thus, most of its episcopal sees lie directly on the so-called "limes", in military camps which became towns. In addition, the episcopate was the most stable and durable Roman institution in the region, since it was the only one to survive the successive invasions. Nevertheless, the question of Christianisation has not resulted in any complete synthesis since Jacques Zeiller's "Les origines chrétiennes dans les provinces danubiennes de l'Empire romain" (Paris, 1918). Thus, the DANUBIUS project will reconsider the question in the light of the scientific advances made in the last hundred years, both in terms of archaeology and history, for the period between the 3rd century, which saw the first evidence of the existence of a clergy in the region, and the 8th century, during which the Byzantine episcopal hierarchy gave way to a new ecclesiastical order. It would be clearly impossible to study all the Danubian provinces in only three years. Therefore, this project - which is the first stage of a long-term research program - is focusing on the last reaches of the Danube to be lost by Constantinople, which is also the part of the river which is best documented from literary sources, viz. the Lower Danube (the Late Roman provinces of Dacia Ripensis, Moesia Secunda and Scythia). To do so, it has been decided to develop a geographic information system (GIS) model of the episcopal sees and other Christian sites, structured around three axes. The first axis foresees the establishment of an analytic database of the sources of Christianity in the Lower Danube. This database, which will bring together all material and written published traces of that religion, will constitute the main core for the development of the GIS model, with the intention that it should be at the same time useful to archaeologists, historians and epigraphists. The second axis is planned around the archaeological explorations of the Late Roman fortress of Zaldapa (Krushari, Bulgaria), through conventional excavations, as well as non-invasive techniques of investigation. The field results of that case study, which began in 2014, will complement the database of the first axis. The third axis was conceived in order to offer a first historical interpretation of the sources collated in the first axis database, through the compilation of a Christian prosopography of the Lower Danube, while offering the foundation for a historical study of its ancient ecclesiastical organisation. Two formats will be produced: 1- a computer database is planned for the period between the 3rd century and the year 787; 2- a printed version, extending to the whole "Dioecesis Thraciarum", will be derived from that database, stopping in the year 641, as a volume of the "Prosopographie chrétienne du Bas-Empire" series. All these tools will bring us closer to a "total history" of the Christianisation of the Eastern Danubian provinces of the Roman Empire, as that history will be studied in the light of archaeological testimonies and the latter will be analysed with regard to the written sources.