北京的“地下长城”始建的年代跨度很大,最早是宋辽时期,其后是抗日时期,再其后是文革时期,都是出于军事目的。“地下长城”当然是形容词,实际类别是地道。三处地道或说地下长城构成了北京多姿多彩的地下世界。这个世界负载着历史的信息,也负载着历史的沉重。 The “Great Wall of the Earth” in Beijing was built with a spans of age. It was originally the Song and Liao periods, followed by the Anti-Japanese period, and then the Cultural Revolution, all for military purposes. “Underground Wall” of course is an adjective, the actual category is authentic. Three authentic or underground walls constitute the colorful underground world of Beijing. The world is loaded with historical information, but also load the heavy history.