When viewed historically, geographical concepts are seen to have come from an immense variety of sources. They have sprung partly from activities that cause men to travel over the surface of the earth: war, commerce, pilgrimage, diplomacy, pleasure. They have also sprung from the accumulated learning and lore of preceding ages and to no small extent from unfettered flights of the imagination. The history of geography, therefore, leads its students into many fields, affording them a key by means of which they may gain a sounder understanding of the extensive ranges of human activity and of the evolution of important phases of intellectual life. This book is an attempt to illustrate and trace the origins of the most characteristic geographical ideas current in Western Europe at the height of the Middle Ages. Historians of geography have tended to neglect this period partly because of the dramatic appeal of the great Age of Discovery which was immediately to follow. It should be remembered, however, that, small as the known world was during the Middle Ages and naïve as may have been men’s conceptions of it, medieval learning was none the less the central element in the scholarly background of the Age of Discovery. The Renaissance brought no sudden and complete emancipation from old modes of thought. While medieval science persisted and some of its errors may have restricted subsequent progress, on the whole the positive achievements of the fifteenth and sixteenth centuries would have been impossible had it not been for the enlightenment transferred from the centuries that went before. C. R. Beazley in the second volume of his great work, _The Dawn of Modern Geography_ (1901), adequately treats of the travels and explorations of the twelfth and early thirteenth centuries, but to the more theoretical aspects of geographical knowledge in this age he gives but meager space. Karl Kretschmer in a monograph, _Die physische Erdkunde im christlichen Mittelalter_ (1889), deals systematically with the physical geography of the entire Middle Ages but necessarily slights or wholly neglects many of the more interesting writings of the century and a half to which the present book is devoted. Other, lesser studies of the geographical conceptions of this period have to do exclusively with points of detail. The present writer ventures to hope, therefore, that there is place for a book in which the geographical lore of the time of the Crusades is discussed with greater fullness and at the same time with an orientation differing in many particulars from that of any work hitherto devoted to the subject.