Why no sign on the Shanhaiguan of Great Wall of China-Annieli tours

Annieli tours’s Beijing Tour Guide answer:
Shanhaiguan,lying in Qinhuangdao(located in the northeast of Hebei province), is neighbouring to Yanshan Mountain and Bohai Sea and is an important pass in the Great Wall of China. Shanghaiguan is the east start of the Great Wall of China(Great Wall of the Ming Dynasty). There's something written on Shanghaiguan Tower:the First Pass under Heaven. But if you take a close look at the words, you will find that there is no sign under the words. Why no sign? Note:In ancient China, a man of eminence usually wrote his name after inscriptions(to be continued).

    1st part of the Origin of “the First Pass under Heaven” is over.

                                           Wrote by Annieli tours’s Beijing Tour Guide