The Summer Palace is the palace and garden of the Qing Dynasty. Its predecessor, Qingyi Garden, is three mountains and five gardens (three mountains refer to Longevity Mountain, Xiangshan Mountain and Yuquan Mountain). Three gardens, Qingyi Garden, Jingming Garden, and Changchun Garden and Yuanmingyuan Garden, were built on the three hills. The last one was built in 1750. It covers an area of 290 hectares and covers about three quarters of the water surface. Before Qianlong's succession, four large imperial gardens had been built in the western suburbs of Beijing. The four gardens, from Haidian to Xiangshan, had their own systems and lacked organic connections with each other. The "Wengshan Po" in the middle became an open area. In the fifteen years of Qianlong reign, Emperor Qianlong used 4.482 million silver to rebuild Qingyi Garden for the filial piety of his mother and holy queen. With this as the center, the four gardens on both sides were linked together to form a 20-kilometer royal garden area from the present Tsinghua Garden to Xiangshan.