The most detailed early account of life in Asia was written by a Flemish Franciscan monk named William Rubruck (Willem van Ruysbroeck, c.1210-1270). While on crusade with King Louis IX of France, in Palestine he met a Dominican sent by the pope to enlist the Mongols' aid against the Muslims. Rubruck decided he would try to convert the Mongols to Christianity.
He set out in 1253 on a round-trip journey that took him three years, traveling as far as the Mongol capital of Karakoram; he was the first European ever to visit it—that is, who also returned to write about it. His personal mission gave him the opportunity to write about what he saw and the ethnicities and religions and customs he observed.
It is interesting that, as he traveled, he often found other Europeans who recognized his Order because of his clothing. He was also questioned frequently about his "version" of Christianity. He met several Christians and Christian priests who were Nestorians. Nestorius (386-451) was a patriarch of Constantinople who claimed Jesus had two distinct natures: a human nature and a completely divine nature, referred to as Logos. These two natures, or essences, are connected but unmingled. When Nestorianism was condemned in 431 at the Council of Ephesus, the Assyrian Church refused to change their support for it. Rubruck had his work cut out for him: preaching Christianity, and preaching against the local Christianity.
There's more to say about Rubruck, but I'll leave off for today with a simple thought: if he had become more famous than the other guy, would there be a game now where people called out "William!" "Rubruck!"