长城词典·关城长城关口上、关口内所建的封闭性军事设施。既用于驻扎守关军队，又用于防御守关。有的与长城相连，长城城墙即作为关城的一面墙；也有的建在关内，距关口数里之遥。平地的关城多为方形或长方形，如山海关等；山地的关城则根据地形和防御需要设计平面，如古北口的关城居两山之间，紫荆关关城为不规则的五个小城组成。 Great Wall dictionary·Pass TownPass town，the closure military facility built on top or inside the pass gate，is used both for stationing garrison troops and defending the pass. Some of the pass towns are built in connection with the Great Wall，utilizing one of its walls as the pass wall；and some others are built inside the pass，which are several kilometers away from the pass gate. Take Shanhai Pass as an example，most of the pass towns constructed on plains are square and rectangular in shape whereas the flat surface of pass towns built on mountainous region is designed in accordance with their geographical and defensive needs. For instance，the pass town of Beigukou is located between two mountains，and the pass town of Zijing Guan consists of five irregular small towns.
