Introduction to the Upper Pool of the Second Spring: The water system of the Second Spring includes the upper, middle and lower pools. The upper and middle pools are located in the spring pavilion. The upper pool is round, 1.94 meters deep, with an octagonal stone railing, each side of which is 0.80 meters long; the middle pool is adjacent to the upper pool, only 0.65 meters apart, square, and about 1 meter deep. The square stone railing on each side is 1.40 meters long. The two pools are shaped like a round sky and a square earth, and are connected by a water inlet above the pool. Because Zhao Gou, Emperor Gaozong of the Song Dynasty, once drank from the spring here in the Xinsi year of Shaoxing (1161), "therefore a fence was set up to protect it." However, the bluestone fences that exist now are all relics of the Ming Dynasty.