According to legend, at the end of the Western Han Dynasty, in 5 AD, Sima Wangmang threw himself into the ruling and opposition, poisoned the last emperor Han Ping, who was only 14 years old, and usurped the throne. In the name of "Reviving the Han Dynasty", Liu Xiu led outlaws to fight against Wang Mang. The two armies fought fiercely in Baihetan. Liu Xiu was defeated and chased by Wang Mang's army. Liu Xiu fled to the deep mountains in the northwest (now it is the first stone gate of Forgotten Valley). Seeing Wang Mang's pursuers approaching, the front was blocked by the Rocky Mountains. When Liu Xiu was cornered, he shouted, "Who can save me?" Suddenly, the stone gate opened with a bang, and Liu Xiuxi fled with joy. Less than 100 meter, I was blocked by the Rocky Mountain. At this time, Wang Mang's pursuers came, and Liu Xiu called again, "Who can save me?" Suddenly, I heard a boom in Shimen, and Liu Xiu hurriedly got out of the way. Walk less than 300 meters, met a stony mountain, pursuers are approaching. Liu Xiu shouted again: "Who can save me?" . Then, with a bang, the stone gate opened, and Liu Xiu fled in a hurry and fled to a hundred meters away. Rocky Mountain blocked Liu Xiu's way for the fourth time. Liu Xiu let out a cry, stone mountain did not move, follwed pursuer has arrived. Liu Xiuzhen sat on the stone chair split by the accompanying general Geng Yan and sighed, "Heaven will destroy me."
Just listen to twittering, a flock of swallows flew over the sky, and a plank road was cracked on the cliff. Liu Xiu led the others along the plank road towards the top of the mountain in the direction where the swallows came. At this time, the swallow disappeared, and I saw a cave in front of me, that is, Lei Zhenzi Cave. Liu Xiu led the beaten army into the cave, and the boulder at the mouth of the cave collapsed and covered the hole, blocking Wang Mang's pursuers and preparing to dig a pit to chase Wang Mang.
A few years later, Liu Xiu led 30,000 soldiers and horses, and defeated Wang Mang's 420,000 troops, and won a great victory in Kunyang (now Yexian County, Henan Province). In the first year of Jianwu (10), in AD 25, Liu Xiu changed to Luoyang, the capital of the Eastern Han Dynasty, and was known as Emperor Guangwu. In order to commemorate the strict guide during the disaster, this mountain was named Yanzi Mountain, the four stone gates were named Ximen, Caimen, Fumen and Transfer Gate respectively, the Shendao Road was named Tiandao Road, the Lei Zhenzi Cave was named Yanzi Cave, the boulder at the entrance was named Tuishi, the stone chair was named Dragon Chair, and the valley was named Forgotten Valley.