** FILE ** In a file photo Chinese hikers walk on a crumbling section of the Great Wall of China north of Beijing on the last day they were legally allowed to do so Thursday July 31, 2003. sections of the Great Wall of China are being reduced to "mounds of dirt" by sandstorms and may disappear entirely in 20 years, a report said Wednesday, Aug. 29, 2007. (AP Photo/Greg Baker)