This essay reconstructs a largely forgotten project by a group of late sixteenth‑century Ottoman intellectuals to challenge traditional cosmographic knowledge, and to introduce the principles of modern mathematical cartography, through the systematic engagement with material from recently published Italian printed texts. It does so by comparing three different manuscript versions of Sipahizade Mehmed’s Kitāb‑ı Evẓaḥ al‑Mesālik ilā Maʿrifeti’l‑Buldān ve’l‑Memālik (The Conspicuous Pathways to Knowledge of Kingdoms and Countries), an encyclopaedia of world geography that the author progressively developed and rewrote over the course of nearly two decades, between the early 1560s and the 1580s. The final of these versions, containing the most radically new ideas on world geography, exists today in a single, incomplete copy from the eighteenth century – possibly an indication that its content was considered politically unpalatable by Sipahizade’s most influential colleagues.