Cosmography, understood as a form of geography, is the written and graphic representation of the Earth, the seas, peoples, and their history. Between the lower Middle Ages and the early Modern Age, the science of cosmography developed into a cultural synthesis of Christian cosmology, Aristotelian natural philosophy, Ptolemaic astronomy, and written and oral narratives by travelers, monks, merchants, diplomats, and ship pilots. From the late thirteenth century on, oral knowledge became a key resource for verifying and updating information transmitted through written sources. The physician and philosopher Pietro d'Abano (1250-before 1318) regarded Marco Polo's narratives (1254-1324) as reliable testimony. Similarly, the major cartographers of the period, from Fra Mauro (?-1459) to Martin Behaim (1459-ca. 1507), relied on reports by travelers to the remotest regions of the known world when drawing their maps. Toward the mid-sixteenth century, Battista Ramusio (1458-1557) and the cartographer Giacomo Gastaldi (ca. 1500-1566) undertook a critical comparison of ancient and modern sources with information from Portuguese and Spanish pilots passing through Venice. The same method was adopted by the cosmographers of the Casa da Índia in Lisbon and the Casa de Contratación in Seville, who were in charge of preparing the official maps for the political and trade expansion of the two kingdoms and for the discoveries of the New World.