About a millennium ago, in Cairo, someone completed a large and richly illustrated book. In the course of thirty-five chapters, our unknown author guided the reader on a journey from the outermost cosmos and planets to Earth and its lands, islands, features and inhabitants. This treatise, known as The Book of Curiosities, was unknown to modern scholars until a remarkable manuscript copy surfaced in 2000. Lost Maps of the Caliphs provides the first general overview of The Book of Curiosities and the unique insight it offers into medieval Islamic thought. Opening with an account of the remarkable discovery of the manuscript and its purchase by the Bodleian Library, the authors use The Book of Curiosities to re-evaluate the development of astrology, geography and cartography in the first four centuries of Islam. Early astronomical maps' and drawings demonstrate the medieval understanding of the structure of the cosmos and illustrate the pervasive assumption that almost any visible celestial event had an effect upon life on Earth. Lost Maps of the Caliphs also reconsiders the history of global communication networks at the turn of the previous millennium. Not only is The Book of Curiosities one of the greatest achievements of medieval map-making, it is also a remarkable contribution to the story of Islamic civilization.