This paper revisits Claudius Ptolemy's depiction of Germania Magna through a multidisciplinary approach, integrating computer-aided distortion analysis of Donnus Nicolaus Germanus's medieval cartography with geological insights. The study proposes that the region underwent significant and complex transformations, likely influenced by tectonic activity, such as the reactivation of the Caledonian Deformation Front (CDF), a major geological structure in Europe that separates ancient orogenic belts, and possibly by cosmic events like the Chiemgau impact, a proposed meteorite impact in southern Germany. A reevaluation of Germanus's map, aligned with modern cartographic data, challenges long-held interpretations of Germania Magna's boundaries. The analysis suggests that Ptolemy's Vistula Fluvius corresponds more closely to the present-day Schwarze Elster in Germany rather than the Vistula River (Weichsel) in Poland. Building on this reinterpretation, the study further examines the potential regression of the Oceanus Germanicus, attributing it to tectonic shifts, volcanic activity, or changes in relative sea level. These environmental processes may have profoundly shaped settlement patterns and cultural development, influencing not only coastal areas but also extending to all regions of Germania Magna, as communities presumably adapted to substantial environmental changes. By situating Germania Magna within the broader framework of geological, cosmic, and climatic phenomena, this study offers new insights into pivotal events and processes that could have shaped the environmental and cultural landscape of Northern and Central Europe in antiquity. It aims to encourage further interdisciplinary research and a critical reassessment of historical and archaeological interpretations.