Gog and Magog, the apocalyptic destroyers prophesied in the book of Revelations, gave concrete expression to the apocalyptic climate that dominated medieval thinking about the future-and the present. They permeated medieval texts and appeared in most maps of the world. Historians are coming to understand medieval and early modern world maps not primarily as rather primitive technical tools but as cultural documents. Such maps expressed in graphic form the world view(s) of medieval elites (princely, scholarly, mercantile). The traditional contents of mappaemundi and early printed maps place them firmly in the tradition of medieval learning, yet they show signs very early on of skeptical and "empirical" questioning directed at received (mainly ancient) wisdom concerning the existence, location, population, and qualities of traditional cartographic *topoi (e.g., the kingdom of Prester John). As Renaissance source-scholarship, rules of evidence, and overseas exploration reshaped cartography, world maps underwent both a rapid transformation into sources of up-to-date information and a certain retrenchment of traditional contents, especially in distant and marginal areas. Gog and Magog are among the principal remnants of the medieval dream of the world. They appear, often with reference to Marco Polo, on world maps well into the seventeenth century. Early modern Europeans continued to view much of the world through medieval lenses.