Beijing Yanqing Wulong Canyon scenic spot was formerly known as Black Dragon Pool. It is located in the downstream of the Black River, and belongs to the Mesozoic volcanic lava area which is 140 million years old. The canyon is 2 kilometers long and is a typical landscape of deep river valley in the mountains. Both sides of the canyon have steep walls, strange rocks and roaring water, and the canyon is famous for its green hills and deep pools. The cliffs are steep and the pools and streams are connected. There are fourth pool, third pool, second pool and head pool in order. Among them, the head pool is relatively wide and the four pools are the deepest. Every year when the water is abundant, the river rushes down from the cliff of several dozen meters high and stirs between the boulders in the mountain stream. You can see the waves hitting the rocks, splashing water, and hear the thunderous sound of the waves like lions roaring. It is quite spectacular.