【正文】
atchtower at Badaling standing on a hilltop, is reached only after a steep climb, like climbing a ladder to heaven. The view from the top is rewarding, hoverer. The Wall follows the contour of mountains that rise one behind the other until they finally fade and merge with distant haze. A signal system formerly existed that served to municate military information to the dynastic capital. This consisted of beacon towers on the Wall itself and on mountain tops within sight of the Wall. At the approach of enemy troops, smoke signals gave the alarm from the beacon towers in the daytime and bonfire did this at night. Emergency signals could be relayed to the capital from distant places within a few hour long before the invention of anything like modern munications. There stand 14 major passes (Guan, in Chinese) at places of strategic importance along the Great Wall, the most important being Shanghaiguan and Jiayuguan. Yet the most impressive one is Juyongguan, about 50 kilometers northwest of Beijing. Known as Tian Xia Di YI Guan (The First Pass Under Heaven), Shanghaiguan Pass is situated between two sheer cliffs forming a neck connecting north China with the northeast. It had been, therefore, a key junction contested by all strategists and many famous battles were fought here. It was the gate of Shanghaiguan that the Ming general Wu Sangui opened to the Manchu army to suppress the peasant rebellion led by Li Zicheng and so surrendered the whole Ming empire to the Manchus, leading to the foundation of the Qing Dynasty. (16441911) Jiayuguan Pass was not so much as the Strategic pass Under the Heaven as an important munication center in Chinese history. Cleft between the snowcapped Qilian Mountains and the rolling Mazong Mountains, it was on the ancient Silk Road. Zhang Qian, the first envoy of Emperor Wu Di of the Western Han dynasty (206 ), crossed it on his journey to the western regions. Later, silk flowed to the west through this pass too. The gatetower of Jiayuguan is an attractive building of excellent workmanship. It has an inner city an