The Great Wall was constructed over a period of many centuries starting from the three kingdoms period and completed by the Mings, some 2000 years later in the 17th century. Most of the current Great Wall is built by the Mings and much of the parts built earlier during Qin and three kingdoms period, using wood, small stones and mud, has crumbled away apparently.
Frankly, I'd rather substitute the Great Wall with the Mogao Grottoes (Thousand Buddha Caves). IMO, as awe inspiring if not more.
http://www.chinatravel.com/china-travel-gu.../dunhuang.shtml