Transmission of knowledge between Islamic and Western cultures has often been presented in terms of ‘influences’, as part of a general process of scientific progress. But do geography and maps belong to science or to culture? How can the historian recognize the cultural origins of geographical knowledge? The Catalan Atlas (Bibliothèque nationale de France, MS. Espagnol 30) is one of the most famous cartographic artefacts of the Middle Ages. It was completed ca. 1375, and was part of the library of King Charles V of France by 1380. It is generally attributed to the Jewish cartographer ‘Cresques Abraham’, ‘master of compasses’ in Palma de Majorca. The Catalan Atlas, composed both from medieval mappae mundi and nautical maps, offers a well-documented representation of the whole inhabited world, as it was known in fourteenth-century Europe, from England to China. Although several studies have underlined the links between the Catalan Atlas and Marco Polo, the direct or indirect Islamic sources of the Atlas have been mainly underestimated. The mix of pluricultural sources in the Catalan Atlas can be explained in the light of merchants’ archives, and by the position of Majorca as a center of international cultural exchanges during the fourteenth century.