What is the Eight Doors of Hongdu (Qing Dynasty) and why did Zhu Yuanzhang occupy Qing Ji?

This is the nine gates in the period of defending Hongdu in the late Yuan Dynasty and early Ming Dynasty. New City Gate, Zhangjiang Gate, Watergate, Qiaobu Gate, Tubu Gate, Gongbu Gate, Fuzhou Gate, Liulimen Gate and Dan Tai Gate.

Qing Ji, Nanjing, Why Occupy Nanjing: Excerpts from Those Events in the Ming Dynasty

The country is too small.

Zhu Yuanzhang felt urgent about this, and this small county town could not have great development. His eyes turned to Qing Ji. Superstition is a common problem in feudal times. If you want to occupy the world, you must first occupy the land of kings. Nanjing is such a place. Purple Mountain runs through the north and south, just like a dragon lurking, while the rocky mountain is steep on the river, just like a tiger. This is the origin of Nanjing Dragon and Tiger. In addition, there is a Yangtze River in front of Nanjing. The emperor, like us, always looks at Feng Shui before buying a house. Nanjing is surrounded by mountains and waters, and feng shui is really amazing. Before the Ming Dynasty, six dynasties established their capitals here. In the Yuan Dynasty, this place was called Qing Ji Road. Not only is the terrain dangerous, but it is also rich in resources.

Nearby is not only an important grain producing area, but also a commercial center. The most important thing is that there is a canal here. In that era when it took several months to walk from Beijing to Nanjing, waterways were really important.