Overseas Wushan has natural phenomena such as Daiyu, Qiao Yuan, Fanghu, Yingzhou and Penglai. According to Liezi Tang Wen, hundreds of millions of miles east of the Bohai Sea, there is a big valley without a bottom, which is called Hui Gui. Hundreds of millions of miles east of the Bohai Sea, there is a deep trench, which is really bottomless. There is no bottom under it, which is called' returning to emptiness'. There are five sacred mountains, namely Daiyu, Qiao Yuan, Fanghu, Yingzhou and Penglai. Each holy mountain is three years high in Wan Li, and the distance between mountains is 70,000 li. Penglai, the abbot and Yingzhou were vividly depicted in Shan Hai Jing and Feng Chan Shu, which led Qi Weiwang and Yan Zhaowang to send explorers to the sea to find the sacred mountain, while Qin Shihuang toured east to collect herbs, and Han Wudi visited immortals. According to historical records, there are often sea cities in the north of Penglai, which are scattered into gas and gathered together, illusory and unpredictable. Those kind alchemists used the illusion and magic of Haicheng to interpret the legend of going to sea on Wushan Mountain, and described a lifelike fairy world that the world yearned for.