Briefly stated, the sources of Leardo’s geography are to be sought in the information accumulated by the Greeks and Romans, as added to and altered during the early Middle Ages by the Church Fathers on the basis of the interpretation of the Bible and as later augmented by the work of medieval travelers, merchants, and sailors. At a very early period the Greeks developed the idea (borrowed, perhaps, from the Babylonians[16]) that the earth is a flat disk surrounded by the Ocean Stream. This conception seems to have given rise to a cartographic tradition followed by certain ancient and medieval map-makers who had long outgrown the belief that the earth is actually flat. Thus Leardo draws a circular land mass, or _oikoumene_, surrounded by a narrow hem of water. We cannot, however, question his belief in the sphericity of the earth, for otherwise he could hardly have held the views expressed in the panel below the calendar. Furthermore, his two legends relating to the fiery and frozen deserts echo a theory that was propounded in classical times and based on the hypothesis of a spherical earth. This theory, worked out in detail by Crates of Mallos, is briefly as follows.[17] Around the equatorial circumference of the globe is a fiery zone so intensely hot that no man can cross it. This zone cuts off all communication with the southern hemisphere. The north and south polar caps are uninhabitable because of the cold. An ocean encircling the globe from north to south intercepts communication with the half of the northern hemisphere opposite the _oikoumene_. Many maps were made in the Middle Ages to illustrate this conception. Leardo presumably had it in mind and did not intend to represent either a flat disk or a complete hemisphere but merely a circular portion of the earth’s surface lying north of the equator. In its orientation, with east and the Terrestrial Paradise at the top and with Jerusalem at the center, the map follows the Christian tradition of the earlier Middle Ages. Other features reflecting the influence of the Scriptures are Noah’s Ark resting on top of Mt. Ararat, Mt. Sinai, the exaggerated length of the River Jordan, and an inscription in the far northeast referring to Gog and Magog. Later medieval contacts between Europe and remote lands are revealed in names derived from Marco Polo and possibly from other Western travelers who had visited the Orient, as well as in the Arabic names in Asia and Africa.