Introduction to Tiexuoxiongguan: Tiexuoxionguan, about fifteen miles west of the city, is commonly known as Datieguan. It has two peaks facing each other, as if it were made of iron. It is next to the Maokou River. The ancient road winds down, getting steeper as it goes down. : Looking up at the dome rock cliffs, the situation is extremely dangerous; looking down into the ravine, the green trees are misty, like green waves and mist, deep below. Dozens of miles up and down, they are all dangerous places. In ancient times, they were the strategic points of military affairs in Yunnan and Guizhou. In the twelfth year of Tongzhi, Sima Yuhuai of Langdai wrote a letter with the words "Yanjiang Lock Key" carved on the half-rock wall, which can still be vaguely seen today.