"Three mountains and a half fall out of the sky, so Egret Island divides the river." The "Three Mountains" are located on the Yangtze River in the southwest of Jinling. The three peaks are juxtaposed and connected with the north and south. Lu You's Book of Entering Shu says, "Sanshan Mountain, Zishi Mountain and Fenghuang Mountain, is there a middle ear?" And after that, it's only more than 50 miles from Jinling. "Lu You's" presence or absence "just means" falling into the sky ". Li Bai wrote the half-hidden and half-present of the three mountains just right. " Egret Island ",on the west Yangtze River in Jinling, divides the Yangtze River in two, so it is called" the island where egrets divide the river ". These two poems are magnificent and neat, and they are rare good sentences.