Great Wall of ChinaChinese Wanli ChangchengDefensive wall, northern China.One of the largest building-construction projects ever carried out, it runs (with all its branches) about 4,000 mi (6,400 km) east to west from the Bo Hai (Gulf of Chihli) to a point deep in Central Asia. Parts of the fortification date from the 4th century BC. In 214 BC Shihuangdi connected existing defensive walls into a single system fortified by watchtowers. These served both to guard the rampart and to communicate with the capital, Xianyang (near modern Xi'an) by signalsmoke by day and fire by night. Originally constructed partly of masonry and earth, it was faced with brick in its eastern portion. It was rebuilt in later times, especially in the 15th and 16th centuries. The basic wall is about 30 ft (9 m) high, and the towers rise to about 40 ft (12 m). It was designated a UNESCO World Heritage site in 1987. 长城 亦称万里长城(Wanli Changcheng)。 中国北方防御性的屏障，是人类建造的大规模建筑工程之一。东起渤海，向西延伸到中亚深处，若将其支段计算在内，总长约6,400公里(4,000哩)。其中部分堡垒的历史可追溯至公元前4世纪。公元前214年秦始皇将当时存在的城墙，连结成一整套防御体系，并设置了望台增强其功能。了望台既可护卫城墙，并可藉由讯号(白日升烟、夜晚燃放火光)向首都咸阳(今西安附近)传递讯息。长城本来有部分是以石头和泥土建成，但其东段则以砖块覆盖表面。长城于后世续有修建，特别是在15～16世纪。长城的基本高度约为9公尺(30呎)，了望台则高达12公尺(40呎)。1987年长城被列为世界遗产保护区。
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