Why is there an ancient city hidden at the bottom of Qiandao Lake?

First of all, you should know that Qiandao Lake is not a natural lake, and its age is very short. After the founding of the People's Republic of China, because of the construction of Xin 'anjiang Reservoir, all the local people emigrated, and then the water flooded. The islands in Qiandao Lake today are actually many hills there. There were many residents there at that time. Of course, after impoundment, various buildings will be left underwater, including some ancient buildings in Ming and Qing Dynasties. Now it has become an "ancient underwater city".