Photo taken from the 121st floor of the Shanghai Tower on April 1, 2015 shows Shanghai World Financial Center (L) and Jin Mao Tower (R) amid heavy fog in Shanghai.[Photo/Xinhua]

Photo taken from the 121st floor of the Shanghai Tower on April 1, 2015 shows the Oriental Pearl Radio and TV Tower amid heavy fog in Shanghai.[Photo/Xinhua]

Photo taken from the 121st floor of the Shanghai Tower on April 1, 2015 shows Shanghai World Financial Center (L), Jin Mao Tower (R) and the Oriental Pearl Radio and TV Tower (upper) amid heavy fog in Shanghai. [Photo/Xinhua]