Rabban Bar Sauma, Mongol envoy to the pope
Rabban Bar Sauma, 1220-1294 CE, was a Nestorian monk who became a diplomat for the Mongol khan and visited Europe. Born near present-day Beijing, and apparently of Uyghur descent, he embarked on a pilgrimage to Jerusalem, but because of the ongoing conflict between Mongols, Mamluk armies and invading Europeans he was forced to turn back. Instead he spent several years in Baghdad, which at the time was a part of the Ilkhanate. It was from here that he was dispatched to Europe on a diplomatic mission to seek an alliance with the French against the Mamluk rulers in Cairo.
Rabban Bar Sauma began his journey in 1287, accompanied by a retinue of assistants, including an Italian interpreter and some 30 animals. First he crossed the Black Sea to Constantinople where he had an audience with the Byzantine emperor. He then continued on to Italy, sailing past Sicily where he observed a spectacular eruption of Mount Etna. He arrived in Rome, but too late to meet the pope who just had died. Instead he went to Florence, Genoa and Paris where he spent a month as the guest of the French king. In Gascony, which at the time was an English possession, he met the king of England. Both the French and the English were enthusiastic about the idea of military alliance, but the details were difficult to work out. For one thing, the king of England needed soldiers at home to put down rebellions by the Welsh and the Scots.
Going back to Rome, Bar Sauma was received by the newly elected pope who gave him communion on Palm Sunday, 1288. From here he returned to Baghdad with gifts and messages from various European rulers. This is also where he spent the rest of his days, compiling a book in which he recounted his far-flung travels. Rabban Bar Sauma died in Baghdad in 1294. The military alliance between the Europeans and the Mongol khan never happened.
Nestorian Christians, by the way, is the branch of Christianity which expanded in a eastwardly direction already in antiquity, forming thriving congregations in Central Asia, India and China during the Tang dynasty. The Nestorians were independent of Rome and worshiped according to their own rituals. They denied that Christ could simultaneously be both god and man. Today a few hundred thousand Nestorians remain, mainly in Iraq, Syria, Iran and the United States.