Originally known as Yingtianfu, Nanjing City served as the capital during the early Ming Dynasty (1368-1644). The city was famous for its tall, solid and grand city wall that gave it the name First Large City in the world.

Nanjing City wall originally had two parts: the inner and outer rings. The outer wall made of earth was destroyed; the inner brick and stone wall stretched to the southern ridge of Zhongshan Mountain in the east, Shitou in the west, Qinhuai River in the south and Lion Mountain and Jiuhua Mountain in the north. The Nanjing City Wall was constructed between 1366 in the Yuan (1271-1368) and 1386 in the Ming Dynasty.

The inner wall has an irregular shape: it is narrow and long from south to north. It was built according to land shape and defense needs. The wall has an inner perimeter of 33.676 kilometers and is 14-21 meters high, containing 13,616 battlements and 200 fortresses. It is the longest city wall in China, as well as in the world. Using huge stone bars as its base, the wall was built by layering large brick blocks. Each block is about 45-by-20-by-10 cm and weighs between 10 and 12 kilograms. Limewater mixed with polished glutinous rice was used to make a firm bond that enabled the wall to stand upright for over 600 years.

The well-preserved section of the current wall is 19 kilometers long, measuring 25 meters at its highest point with a depth of 23 meters. Only eight out of the 13 city gates remain. Of all the gates, the Treasure Gate, also known as the China Gate, is the grandest.

Built in 917 during the Five Dynasties Period (907-960), the China Gate served as the southern center gate of the capital during the Southern Tang Dynasty. During the early Ming period the gate was rebuilt when the capital was expanded. The rectangular gate is 128 meters long from south to north and 90 meters wide from east to west, covering an area of 11,720 square meters. Originally it had three stories, including a tower, but now only the base remains. The gate has four arched doors of about 19 meters made of brick blocks. Each gateway has a double-leaf wooden door wrapped with iron sheets. A total of 27 stone caves were dug at the south end to serve as storerooms for military supplies and resting places. The biggest cave was large enough to conceal 1,000 soldiers.

The current China Gate witnessed great changes over its 600-year history. It is the largest and most complete fortress-shaped gate in China that holds an important position in the country's architectural history. It provides precious insight into the study of Chinese ancient defense systems and wall architecture.