Toward this end, Khubilai Khan launched a major expedition in 1281 to discover and map the source of the Yellow River, which the Mongols called the Black River. Scholars used the information to make a detailed map of the river. The expedition opened up a route from China into Tibet, and the Mongols used this as a means of including Tibet and the Himalayan area in the Mongol postal system. The new connections did more to connect Tibet—commercially, religiously, and politically—with the rest of China than anything else during the Mongol era.
