This study analyzes the travelogue of Francesco da Collo, an imperial envoy to Moscow (1518–1519), focusing on his representation of Eastern European physical geography. Despite the contemporary refutation of the Riphean and Hyperborean mountains by Mathias de Miechow (1517), Da Collo maintained that these ranges were the necessary sources of major rivers, particularly the Tanais (Don). The author argues that this adherence to classical cartography was driven by a theoretical concern for the stability of the Mediterranean hydrosystem. Believing that the Mediterranean relied on the Tanais, Da Collo argued that such massive water volumes could not originate from lowland marshes but required high-altitude sources. Consequently, he erroneously posited that the Volga flows into the Tanais—and thus the Mediterranean—rather than the Caspian Sea, preserving a hydrographic logic rooted in antiquity.