It has been fashionable in the generalist literature to argue that the Ottomans lacked knowledge in European geography and politics. This chapter first offers some comments regarding Istanbul's understanding of geography and environment in the context of Ottoman strategy and frontier warfare. The, it presents a short overview of the importance of rivers, marshlands and mountains with regard to the formation of the opposing Hapsburg and Ottoman defence systems in Hungary. The last part of the chapter deals with the relationship between landscape, climate and fortifications and offers some preliminary results and tentative observations regarding deforestation and marshlands. The discussion also argues, although in somewhat different ways, that the Ottomans and their Hapsburg rivals both had a keen interest in geography and mapped their empires and resources, and possessed adequate information as to the terrain and river systems of their lands and frontiers.