What were Genghis Khan's acheivements, what were one of his biggest?

Some of his acheivements were that he united nomadic tribes, plus he invaded and conqeured most of Asia/Europe. His empire lasted 150 years, that's a pretty long time, and after he died the empire still stretched. Soon though after he died the empire collapsed and seperated, but one of his biggest acheivements was conquering China.