Tourists view a rainbow over the Hukou Waterfalls, a section of the middle reaches of the Yellow River, in Linfen, north China's Shanxi Province, Dec. 8, 2012. Icicles have been formed on the Hukou Waterfalls recently due to low temperature. Hukou Waterfalls are located on the border of Shanxi and northwest China's Shaanxi Province. (Xinhua/Lv Guiming)