Surface archaeological survey has been widely established as the principal method for the regional study of Mediterranean diachronic landscapes. Before the introduction of GPS and digital, GIS-based recordings in the late 1990s, survey projects employed analogue recording strategies (e.g. personal notebooks, printed forms and cartographic materials) resulting in low-precision spatial datasets. These archives, termed here as legacy survey data, can today be visualized and analysed using computational tools. The aim of the present work is to exemplify how legacy data can be reused and reproduced to explore unknown aspects of past survey projects. It showcases a multi-source, GIS-structured workflow to manage and re-evaluate data from the region of Grevena, north-western Greece, where a largely unpublished all-period extensive survey titled the Grevena Project has pinpointed a rich, yet unavailable to the archaeological community cultural record. The publications lacked critical evaluation of the survey results and significance, such as accurate site locations, size and chronology as well as a description of the field collection strategies used. To recover and combine these data into a single geodataset, a three-step workflow was created, including the systematic recording of collected artefacts, the deployment of archival and remote-sensing resources (e.g. georeferenced cartographic and photographic materials and satellite imagery) and the development of a new extensive survey in selected areas for validation purposes. Results indicated heterogeneity in the techniques employed by the Grevena Project for site recognition. They also brought an important assemblage of Palaeolithic finds unrecorded before. Furthermore, large-scale geomorphological analysis using geomorphometric approaches demonstrated an irregularly high density of sites in elevated areas, which is considered a surveying bias. Remote sensing sources including archival aerial photographs highlighted regional landscape changes (e.g. in forest coverage) revealing architectural remains unmapped before. Finally, the new survey around Ayios Georgios showed the discovery of several new sites, emphasizing a case study of much more complex dynamics than originally considered during the Grevena Project.