Nanjing, also known as the Treasure Gate, is the largest and most complete treasure base urn in China.

The cornucopia of Nanjing Ancient City is the largest and most complete treasure urn in China.

At present, the largest existing city wall in China is the Ming City Wall. Before it was built, the traditional urn in China was placed outside the gate. As soon as Nanjing Ming City Wall broke away from the old system, it set up an urn hole in the city gate, and set up a revolutionary "urn hole" on the city body, which greatly strengthened the defense ability of the city gate. Among the gates in Beijing 13, except for the Toilet God Gate, they are all inner wengcheng, and the scale and momentum of Sanshanmen, Tongji Gate and Jubaomen (now called Zhonghua Gate) far exceed other gates.

Nanjing Zhonghua Gate, located in the south of the city, was originally the south gate of Nantang Capital. Rebuilt in the Ming Dynasty, it is 3 178 meters long, with 1202 stacks in the east and Sanshanmen in the west. The "Zhonghua Gate Castle" that has been preserved now has four walls and 27 hidden soldiers caves, among which there are three enemy towers on the outermost layer, three on the left and right of the city gate, and seven on the second floor foundation, the largest of which has an internal area of 3 10 square meter. These caves are usually used to store military supplies, and more than 3,000 soldiers can be hidden in wartime. Some experts believe that the setting of the inner urn not only enhances the defense of the city gate, but also embodies the Taoist thought of "state-owned weapons, not showing people" of designers and builders.