ModernChineseandinternationalresearchusingnewmethodslikedronessystematicallystudiestheGreatwallofChina.Itsvisibilityfromspaceisalegend,butitssizeactuallyranksasworld'slargestmonument.Itneverwasasinglewall,butasystemofseveralsegments,repeatedlyalteredovertime,insuccessiveattemptstopreventinvasionsfromraidertribes,liketheXiongnu,adaptedtotheterrain,withanelaboratesystemofgarrisontowers,advancedtowerpostsandcommunicationsystem.Buildingandmanningitprovedextremelycostly.ItfailedtopreventtheMongolarmiesofGenghisKhanannexingChina,hisgreatsuccessorKublaiKhanbuiltawallsystemtofithislargerempire.AftertheMingdynastyfinallyexpelledtheMongols,the'primitive'wallswerereplacedbythefinalstoneversion,usingabricktypesolidifiedwithricestarch.Whiletheunprecedentedmobilizationofmeansforconstructionandgarrisonscrippledthetreasury,itproveduselessagainstthe...