This is a folk proverb, which comes from the famous sentence of Lu Guimeng, a poet in the Tang Dynasty: "The Han Dynasty is ancient and expensive, and the mountains and rivers are beautiful in the world." When it comes to Qingcheng Mountain, we will think of the phrase "Qingcheng Mountain is quiet in the world", and when it comes to Emei, we will think of "Emei is the best in the world".
These two sentences originated from Sichuan's "four musts". Since they are "four musts", there are two more sentences behind them. "Four Wonders" is a summary of famous scenic spots in Sichuan, including Qingcheng Mountain, Emei Mountain, Jiuzhaigou and Jianmenguan, so the remaining two sentences are "Jiuzhai is a wonder in the world, and Jianmen is a dangerous place in the world".