In 1644, a Nanjing publisher named Cao Junyi printed a unique world map that he called “a complete map of all under Heaven.” He followed certain Chinese conventions going back to the Song and Yuan dynasties, but he also drew on a European map of the world designed by Ortelius and printed in Nanjing by the Jesuit missionary Matteo Ricci. Copies of this map survive today in two national libraries, one in Beijing and the other in London. The two chapters of this book, originally delivered as the Kuo Ting-yee Memorial Lectures at Academic Sinica, each take one of these copies of Cao’s map as points of departure to reconstruct a history of world maps that looks back to earlier Chinese and European attempts to map the world and forward to the effects that Chinese world maps like Cao’s had on European cartography. This history reveals that Europeans depended on Chinese knowledge of Asia just as much as Chinese depended on European knowledge of world. Out of this interaction emerged the map of the world as we know it today.