Why Yushan Lake in Changshu and Shang Hu are so symmetrical, and what happened in ancient times, please ask people who study geography to explain.

First of all, Yushan is a part of the anticline of a mountain. After the subsequent geological tectonic movement, the mountains around Yushan were cut by faults, and the cut faults gradually subsided, and then the Yushan was formed through orogeny and denudation and deposition. The Jianmen Canyon in Yushan is actually a fault, just as we observed that a lake was formed at the top of Jianmen Canyon opposite the southwest slope of Yushan. We infer that the lake was formed here by cutting the remaining plots under the Yushan settlement and geological action, thus forming the lake opposite Yushan Mountain and the southwest slope of Yushan Mountain.