Great Wall of China the optics much better, rendering photographic evidence irrelevant to the issue of whether it is visible to the naked eye. Great Wall of China The Great Wall of China is a series of fortifications made of stone, brick, tamped earth, wood, and other materials, generally built along an east-to-west line across the historical northern borders of China to protect the Chinese states and empires against the raids and invasions of the various nomadic groups of the Eurasian Steppe with an eye to expansion. Several walls were being built as early as the 7th century BC; these, later joined together and
History of the Great Wall of China the north. Khublai Khan dealt with such threats by using both military blockades and economic sanctions. Although he established garrisons along the steppe frontier from the Juyan Lake Basin in the far west to Yingchang in the east, Khublai Khan and the Yuan emperors after him did not add to the Great Wall (except for the ornate Cloud Platform at Juyong Pass). When the Venetian traveller Marco Polo wrote of his experiences in China during the reign of Khublai Khan, he did not mention a Great Wall. In 1368, the Hongwu Emperor (Zhu Yuanzhang, r.136898) ousted the Mongol-led Yuan dynasty