The mongol empire reached a halt when they encountered the more advanced civilizations of Europe(caucasians). With greater achitechture(castles), better weapons and armors and so forth....

No that's not the case....
Now, in the Mongol Empire, the Supreme Khan was chosen by the military council, the Kurultai. But the council couldn't agree on which of the Khan brothers should take over, so the Mongol armies had to retreat eastward until they had a new leader. By the time they eventually decided on Ogedei's son Guyuk, the military advantage had been lost, and civil unrest had begun forming.
The Empire slowly disintegrated thereafter, as the grandchildren of Genghis Khan started civil wars with each other. Kublai Khan founded the Yuan Dynasty of China; Turkey was taken over by the Ottomans, et cetera.