What are the so-called three corridors and eighteen holes in Lechang Jiufeng?

Lechang Jiufeng (an important town on the border between Fujian and Guangdong), the word "dong" means: surrounded by mountains on all sides, with a plain in the middle, with mountain streams flowing through it. This is a place where Hakka people are happy to live. With such a terrain, people call the nine peaks "dongs", and the nine peaks are called eighteen caves, such as Tangjiadong, Caojiadong, etc. Jiufeng is also the hometown of Xue Yue, a famous anti-Japanese general. In February 2008, Jiufeng Town in Lechang was also one of the places most severely affected by the ice disaster... "Three Corridors": Unknown! The Nine Peaks and Twelve Water Crossings Scenic Area is also very famous. Tourists come here all year round. Nine peaks are beautiful, and one beauty lies in the mountains and rivers. Jiufeng is located about 30 kilometers northeast of Lechang City and is named after nine mythical and beautiful peaks. The names of the nine peaks are "Sanxing Peak, Wuzhi Peak, Xiangri Peak, Yangjiao Peak, Horseshoe Peak, Ziwei Peak, Qingyun Peak, Taiyi Peak and Yunzu Peak" (also known as: Jiufeng has nine peaks, nine peaks, Individual immortals: Wuzhi Peak (Yuyu Immortal), Xiangri Peak (Lingkun Immortal), Qingyun Peak (Qingyun Immortal), Ziweifeng (Wuyun Immortal), Yangjiao Peak (White Crane Immortal), Horseshoe Peak (Feilai Immortal), Yunzu Peak (Yinzixian), Taiyi Peak (Taipingxian), Sanxingfeng (Shilongxian), hence the name). The highest of these nine peaks, Wuzhi Peak, is 1,726 meters above sea level, and the shortest one is 500 meters above sea level. The mountains are complex, with steep and steep peaks, deep canyons, gurgling mountain streams, and meandering rivers. Many adventurers have set foot here in the past. Cheng Fu, the magistrate of Lechang County in the Qing Dynasty, was very interested after visiting Jiufeng Mountain. He wrote a poem called "Residence in Jiufeng Mountain": "Nine rows of dangerous peaks are directly in the sky, and there are people living in the depths of the rocks. Looking at the vast dark sky, the rushing spring water splashes all night long. The outer road is along a stone path, and visitors from the south are far away from the clouds. This trip is just to rush for science, but I love the famous mountains without thinking about returning them. "Nine peaks are beautiful, and the second beauty is the melons and fruits. Jiufeng not only has beautiful mountains and waters, but is also known far and wide as the "Hometown of Fruits." ?