Railway introduction: In Badaling National Forest Park, there is a railway running parallel to the highway. This is the Beijing-Zhangjiakou Railway, which runs more than 200 kilometers from Beijing to Zhangjiakou. Its characteristics are: from the south entrance through Juyongguan, Siqiao, Sanbao, Qinglongqiao and Badaling, the terrain rises greatly. The train cannot go straight up, let alone turn around the mountain, so it can only pass through the mountain.