第1个回答 2016-05-24
GreatWallofChina,fortifications,c.1,500mi(2,400km)long,windingacrossNChinafromGansuprov.toHebeiprov.ontheYellowSea.Thewall,runningmostlyalongthesouthernedgeoftheMongolianplain,waserectedtoprotectChinafromnorthernnomads.Itisanamalgamationofmanywallsbuiltinancienttimes;thefirstunifiedwallwasbuiltinthe3dcent.B.C.bytheCh'indynasty.LaborerswereconscriptedfromalloverChinatobuildit,andmanyofthemdiedduringtheproject.Thewall'spresentformdatessubstantiallyfromtheMingdynasty(1368–1644).Itaverages25ft(7.6m)inheightandis15to30ft(4.6–9.1m)thickatthebase,slopingto12ft(3.7m)atthetop.Guardstationsandwatchtowersareplacedatregularintervals.Theeasternpartofthewallisearthandstonefacedwithbrick,butinthewestitismerelyanearthmound.SuccessiveinvasionsofChinafromthenorthdemonstratedthattheGreatWallhadlittlemilitaryutility.Since1949twosectionsNofBeijinghavebeenreconstructedandareopentovisitors.