北京城位于华北大平原最西北部、太行山与燕山结合部的山前地带。这里是从华北去往东北、西北和蒙古的诸多山间通道的共同起点,又是沿太行山麓从中原到北方的通道的终点。由于华北大平原曾经湖沼密布,只有通过这条通道才可以往来于北京与中原地区之间。在未有铁路之 Beijing is located in the northwestern part of the Great Plains in North China, the junction area between the Taihang Mountains and Yanshan. This is the common starting point for many mountain passes to the northeast, northwest and Mongolia from north China and the end of the passage from the Central Plains to the north along the foot of the Taihang Mountains. Due to the dense lakes and lakes in the Great Plains of North China, only through this channel can they travel between Beijing and the Central Plains. In the absence of the railway