Zhongnanhai is in Xicheng District. It is collectively called "Three Seas" with the North Sea. The Central Sea was opened in gold. In Yuan Dynasty, the South China Sea was excavated in the early Ming Dynasty. The Qing Dynasty and the North China Sea jointly called Xihaizi and were listed as forbidden gardens. Walking into the Zhongnanhai Sea, many people wonder why the Zhongnanhai Sea is called "sea" and clearly it is a lake.