The main objective of the Mapping Byzantine Bithynia Online (MBBO) project is to make accessible a set of information collected during several French surveys carried out in Bithynia, a region in northwestern Turkey extending from the southern shore of the Sea of Marmara to Mount Olympos (Uludağ) and from Lake Apolyont to the Sangarios (Sakarya) River (Fig. 1). MBBO aims to bring together a large amount of historical and archaeological data according to selected themes, to create and manage a spatial geo-database, and to make these data cartographically manipulable through computer queries. Among the case studies integrated into this program, our project is particularly interested in the Byzantine heritage in the region of Bithynia. The approach is firmly anchored in the emerging field of digital humanities applied to archaeological and historical sciences.