Oneofthelargestbuilding-constructionprojectsevercarriedout,itruns(withallitsbranches)about4,000mi(6,400km)easttowestfromtheBoHai(GulfofChihli)toapointdeepinCentralAsia.Partsofthefortificationdatefromthe4thcenturyBC.In214BCShihuangdiconnectedexistingdefensivewallsintoasinglesystemfortifiedbywatchtowers.Theseservedbothtoguardtherampartandtocommunicatewiththecapital,Xianyang(nearmodernXi'an)bysignal
smokebydayandfirebynight.Originallyconstructedpartlyofmasonryandearth,itwasfacedwithbrickinitseasternportion.Itwasrebuiltinlatertimes,especiallyinthe15thand16thcenturies.Thebasicwallisabout30ft(9m)high,andthetowersrisetoabout40ft(12m).ItwasdesignatedaUNESCOWorldHeritagesitein1987.
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.