The Hukou Waterfall, the second largest waterfall in China, is located 165 kilometers to the west of Fenxi City, Shanxi Province, and 50 kilometers to the east of Yichuan, Shaanxi Province. The width of the waterfall changes with the season, usually 30 meters wide but increasing to 50 meters during flood season. It has a fall of over 20 meters. When the Yellow River surges towards the Hukou Mountain, blocked by mountains on both sides, its width is abruptly narrowed down to 20-30 meters. The water speeds up with increasing waterpower. Then it rushes down from the narrow mouth, forming a grand waterfall of 15 meters high and 20 meters wide, as if water is pouring down from a huge teapot. Hence it gets the name Hukou (kettle spout) Waterfall.

Standing on the bank of the Yellow River, people can see the roaring water rushing through mountains and then plunging into a deep pool, really resembling the boiling water in a teapot. The waves stir up masses of smoke and clouds, rising higher up into the sky, with the color changes from yellow to gray and then to blue. The local people call this marvelous scenery smoke rising from the water.

Beneath the waterfall is the Qilangwo Bridge connecting two provinces, Shanxi and Shaanxi. In the sunshine, the mist is refracted by the sunlight to create a rainbow spanning over the water like a colorful bridge.

Source: http://www.chinaculture.org