what distance is there between the guard post of the great wall

I would recommend visiting Mutianyu great wall, which has probably the biggest density between guard posts, roughly 200m between each other. There is direct bus 980 from Dongzhimen Wai bus terminal (it's in sidestreet behind main bus terminal), admission fee it's about 45RMB, you can take cable car to top (60RMB?) and bobsled track down (60RMB?). On both ends of Mutianyu great wall is unrestored overgrown part if you want to see real great wall. This section of GW is also not so tourist as badaling which should be avoided at any cost.