As the capital of the Yuan Dynasty, Ming Dynasty, Qing Dynasty, and the People’s Republic of China, there are many myths and legends about Beijing. The most well-known is that Beijing, like many other ancient capitals, has a “dragon vein” (龙脉), an important fengshui phenomenon that can affect the fate of a nation. According to a more local legend, there is a whole dragon imprisoned underneath the ground in Beijing. The door to its prison is located in downtown Beijing, near the lantern-stringed restaurant street Gui Jie (簋街).
According to the legend, the dragon has been chained underground since the founding of the Ming dynasty when the city of Beijing was built. The ancient dragon had occupied the land of Beijing long before the capital was built, and he was infuriated at the intrusion of his home. He vowed to use his powers to flood the whole city (Chinese dragons command water and rainfall). Anticipating the dragon’s revenge, Liu Ji, a legendary figure with insurmountable knowledge in the mystics, poetry, and strategy among others, asked another legendary figure Yao Guangxiao to defend the city they built while he was gone.
Finally, Liu Ji left Beijing to report the progress to the emperor. With the only person he feared gone, the ancient dragon teamed together with his son. Together, they commanded water to drown the city. Beijing was on the brink of destruction. Yao rushed over to fight the dragons, yet he could not defend against the two dragons’ attacks. Luckily, the General Yue Fei came to his aid. In the end, they defeated both dragons. Yao chained the father into a well at Beixinqiao, and the son into a well at Chongwenmen.
Imprisoned in the well, the ancient dragon inquired Yao when he would be released. Yao promised to let him out when the bridge becomes old. Thus, the place is named “Beixinqiao” (North New Bridge) so it would never age. A temple of Yue Fei was also established to guard the well. As for the younger dragon, Yao told him he would come out when he hears the sounds Dian, an ancient copper instrument that announced the opening and closing of the gate. However, from then on, Chongwenmen became the only gate which uses a bell instead of Dian, so that the dragon won’t ever see the light of day.
Source: www.theworldofchinese.com