thegreatwallwasrenovatedfromtimetotimeaftertheqindynasty。amajorrenovationstartedwiththefoundingofthemingdynastyin1368,andtook200yearstocomplete。thewallweseetodayisalmostexactlytheresultofthiseffort。withatotallengthofover6,000kilometers,itextendstothejiayupassingansuprovinceinthewestandtothemouthoftheyaluriverinliaoningprovinceintheeast。whatliesnorthofbeijingisbutasmallsectionofit。 amapofthegreatwall themapshowsthewallrunningfromjiayupassofgansuprovincetoshanhaipassofhebeiprovince。representativesectionsofthegreatwallbuiltinmingtimesaresituatednearshanhaipass,gubeikouandjuyongpass。 badalingsection thebadalingsectionofthegreatwallsnakingalongthemountainsnorthwestofbeijingwasbuiltatthebeginningofthemingdynastyinthe14thcentury。being7。8metreshighand5。8metreswideatthetopontheaverage,ithasbattlefortsatimportantpoints,includingthecorners。 located10kilometerssouthofthebadalingsectionofthegreatwallandbuiltinan18。5kilometrelongvalley,thepasshasalwaysbeenanimportantgatewaynorthwestofbeijing。thenameisbelievedtohaveitsoriginintheworkersandslavesconscriptedtobuildthegreatwallinancienttimes。cloudterrace,builtin1345,wasoriginallythebaseofapagodaoverlookingthemainroadofthetownofthepass。thearchedgateoftheterraceandthewallsinsidethearcharedecoratedwithcarvings。ofelephants,lions,birds,flowersandheavenlykingsaswellascharmsinsixlanguagessanskrit,tibetan,phatspa(mongolian),uygur,westxiaandhan。 mutianyusection themutianyusectionofthegreatwall,70kilometersnortheastofbeijing,islinkedtothegubeikousectionontheeastandthebadalingsectiononthewest。itisoneofthebestsectionsofthegreatwall。 themutianyusectionofthegreatwalliscrenelattedforwatchingandshootingattheinvadingenemy。someofthebattlefortsonthewallareascloseas50metresapart。 jinshanlingsection locatedinmiyuncountynortheastofbeijing,thejinshanlingpisionofthegreatwall,likethesimataipision,belongstothegubeikousectionofthecolossaldefencebarrier。 thebattlementsinthejinshanlingpisionofthegreatwallarebuiltalongtheridgeofamountain,wherethesoldierscanresisttheinvadingenemybytakingadvantageofthehighterrain。 adecrepitbattlefortatduskoftenremindsoneofthebattlesinancienttimes。1 simataisection locatedtotheeastofjinshanling,thesimataipisionofthegreatwallis3,000metreslongandhas35battleforts。thewallrisesandfallswiththeprecipitousmountainridge,whilethebattlefortsarelocatedhighupthehills。 alarmwasraisedbymeansofsmokesignals,atnightbyfire。smokewasproducedbyburningamixtureofwolfdung,sulfurandsaltpeter。shotswerefiredatthesametime。thusanalarmcouldberelayedover500kmwithinjustafewhours。