The black-sooted hand of a stone statue at Yungang Grottoes, one of the three major cave clusters in China, is seen March 21, 2007 in Datong, Shanxi Province, China. China's ancient buildings, tombs and stone carvings have weathered storms, invading armies and thieves. Now, they face a new threat, a by-product of the rapid economic development that has lifted so many Chinese out of poverty - the region's growing number of coal-fired power plants.