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 Wall" – were mostly constructed of tamped earth, with some parts built with stones. Where natural barriers like ravines and rivers sufficed for defence, the walls were erected sparingly, but long fortified lines were laid where such advantageous terrains did not exist. Often in addition to the wall, the defensive system included garrisons and beacon towers inside the wall, and watchtowers outside at regular intervals. In terms of defence, the walls were generally effective at countering cavalry shock tactics, but there are doubts as to whether these early walls were actually defensive in nature. Nicola Di Cosmo points out that