The upper reach of Nai River is often called West Stream, and Black Dragon Pool is located beside West stream. The stream falls down from East Baizhang Cliff (trans, Cliff of Hundreds of Meters High, i.e. very high) into a deep pool which used to be called Old Dragon Nest, and forms the first waterfall. Then it falls into another deep pool which is Black Dragon Pool, and forms the second waterfall. To the north of Black Dragon Pool, the 60-meter long Longevity Bridge stretches over East Baizhang Cliff. The iron railings of the bridge are painted red, looking light and attractive.