八达岭长城碗蜒于崇山峻岭之间，依山而建，高低起伏，曲折绵延。八达岭位于居庸关外口，有东、西两座关门，东叫“居庸外镇”，西称“北门锁钥”。关城东窄西宽，长城从“北门钥 锁”关门城合台起依山而筑，城墙高低不一，平均高约7.5米，顶宽约6米，可容五马并驰，十人并行。
该段长城的墙体是用整齐巨大的条石铺成，有的条石长达2米，重数百斤。内部填满泥土和石块，墙顶地面铺满方砖，十分平整。墙顶外侧筑有高1.7米的垛口，上有了望孔，下有射击洞，内侧建有宇墙。城墙每隔一段，筑有一个堡垒式的方形城台。城台有高有低，高的叫敌搂，是守望和军士住宿的地方；低的叫墙台，高度与城墙 相差不多但突出墙外，四周有垛口，是巡逻放哨的地方。在制高点上还设有烟墩，即烽火台，是古代传递警讯的设施。
Badaling Great Wall bowl slug between the high mountain ridge, according to Shan Erjian, the height fluctuation, is continuous windingly. East Badaling located at the Juyongguan collar extension, has, west two to close, east calls “to occupy the commonplace outside town”, west calls “the key to defense of the north”. East Guan Cheng narrow west extends, Great Wall closes the city from “the north gate key lock” to gather Taiwan according to Shan Erzhu, the city wall height varies, erage high roximately 7.5 meters, goes against the roximately 6 meters widely, may accommodate five Ma Bingchi, ten person of parallel. the this section of Great Wall's wall is becomes with the neat giant long and narrow stone shop, some long and narrow stones are 2 meters, the weight several hundred catties. The internal stuff soil and the stone, the wall goes against the ground to overspread the square brick, is very ***ooth. The wall goes against the flank to build has the height 1.7 meters crenels, on has the observation hole, gets down has the fire hole, the inside constructs the space wall. A city wall every other section, builds has a fortress-like square shape tower on a city wall. The tower on a city wall has Gao Youdi, high is called the enemy to hug, is keeps watch with sergeant the lodging place; Low is called the bench table, highly with city wall difference not many, but outside the prominent wall, all around has the crenel, is place which the patrol stands sentry. Is also equipped with the ***oke pillar in the commanding point, namely the beacon tower, was the ancient times tran***its the danger signal the facility.
中国长城的一段。位于北京市延庆县西南部。八达岭地处居庸关关沟北口 ，地势高峻险要，具有重要的战略地位，八达岭长城修筑得格外坚固。其关城有东西两座关门，东门额题“居庸外镇”，西门额题“北门锁钥”，建于明弘治十八年（1505），嘉靖、万历年间曾加以修葺。两门均为砖石结构 ，券洞上为平台，台之南北各有通道，连接关城城墙。京张公路从城门中通过，为通向北京的咽喉。从北门锁钥城楼左右两侧，长城沿山脊延伸，依山而筑。城墙高低不一，平均高度约7.5米，墙的下宽约6.5米，顶上宽约5.8米。可容五马并骑，或士兵十人并行。城墙下为条石台基，上部为巨砖墙壳，内部填以黄土和碎石。墙顶地面铺砌方砖，顶部内侧为宇墙，外侧为垛墙 ，垛墙上有垛口（望口）和射洞，用以镃望和射击敌人。
城墙上每隔 30～40 米或100～200米，于险要处筑一堡垒式堡台。堡台建筑于山脊的高处、城墙的转角处或险要之地。堡台有高有低。高的叫作敌楼，上层有垛口可以镃望射击，下层有券洞、射口可以住宿、射击 、屯储火药和粮食。低的为墙台，高度与城墙差不多，但突出于墙外，四周有垛口，是巡逻放哨的地方，原来上面还有房屋建筑用于士兵休息，现仅存地基。
在八达岭城墙向外眺望，远处还有零散的烟墩，上筑垛口 ，是守卫八达岭长城的警戒设施 。出北门锁钥关门不远，有明隆庆五年（1571）筑成的一座砖城，名岔道城，是八达岭前哨指挥处所在，可驻军 800 余人，并可储备大量的军械于此。八达岭长城在明代盛极一时，到清代后就失去其防御的历史作用，不再修葺。经多年风雨侵蚀和人为破坏而日渐荒芜。1949年以后曾多次整修八达岭关城、关门及南北各4个敌台。18年又重建了居庸关外镇的城楼。八达岭居庸关，翠岭重叠，花木葱茏，早有居庸叠翠之称，古代燕京八景之一，是闻名中外的旅游胜地。
在很久以前，从祁连山流下来的雪水，不断汇合成北大河，它穿过河西走廊中段的荒原，浇灌著那一带的良田，养育著那里的各族人民。有一天，一个牧童正在荒原上放羊，迎头碰上一个古怪老头儿，身上背一袋子石沙，问他去北大河如何走，并说："这北大河原是我的家，后来被一群百姓抢去,我这次来要用石沙堵住北大河。"牧童听后非常气愤，立刻顶撞道："别说你用一袋石沙，就是把北边大山搬来，也妄想使北大河改道。"那老头儿一听气炸了，立刻将这袋石沙向左右撤开，骤然间，荒原上突起许多丘陵和一座大山，这座大山就是现在的嘉峪山。原来这个怪老头儿是龟精变的，只见他口念咒语，企图推倒嘉峪山来封堵北大河，正在此时，突然狂风大作，电闪雷鸣，玉皇大帝派雷神把老头儿击死了。在他死的地方，立即隆起了个山包，形状如龟，这就是现在的"龟盖山"。
