You may be thinking of Rabban Bar Sauma, who visited Paris in the 13th century. He was a Christian from Mongol-ruled China although he might not have been a Mongol himself. There are some previous answers about him:

u/The_Manchurian wrote about South and East Asians in medieval Europe

and European travelers into China and the far east like Marco Polo are well-documented. Were there ever Chinese explorers that traveled as far as Europe? by u/y_sengaku