The city wall of the palace city is the innermost wall among these four layers of city walls.The palace city is also known as the Forbidden City,Danei and inner palace.It is located in the east corner of the city and the central part of the imperial city,where the emperor lives,conducts affairs for the imperial government,and accepts pilgrimages of Chinese and foreign ministers and members of the royal family live.
The city wall of the imperial city is the second layer of wall from the inside out.The imperial city is also known as the inner city and Danei.It is located in the east of the capital,surrounding the palace city and is home to the central administration and national ancestral shrine sacrifice,such as the Imperial Ancestral Temple and Altar of Land and Grain.
The city wall of the capital city is the third layer of city wall from the inside out and is also named as Chenghuang,Now it is named Nanjing City Wall for short,which is the main defense line in Nanjing.The plane layout of the capital city wall breaks through the old system of adopting square and rectangular forms of the ancient cities of China.Considering from the aspect of military defenses.
The city wall of the outer city is the outermost city wall,also known as Waicheng,Luocheng and Guoyuan.It is located at the outer side of the city wall and expands the scope of the military defense of the Nanjing city. The plane layout of the outer city is a diamond shape,It has mountains and rivers in the northwest and hillocks in the southeast.