The lake lies northeast of Nanjing city near the railway station, out of the city wall, and is an enormous urban lake, dotted with causeways and islands. The total area of the park is about 473 hectares (about 2 square miles), which makes it the earliest and biggest comprehensive park in Nanjing. Xiaowu Emperor of the Song Dynasty once inspected the navy on the lake. In the Ming Dynasty, an imperial storehouse was built at Lake Xuanwu for storing national census records and grain tax documents. At the end of the Qing dynasty, it was turned into a park, which occupied an area of 434 hectares with 368 hectares in water. It was said that once a black dragon was seen in the lake. Then it was named Xuanwu Lake, since black dragon was considered God of Water, respected as Xuanwu in Chinese Taoism.
In the lake, there are five isles which are connected by bridges or mounds, each of them having a very attractive and unique flavor. Huan Isle is famous for its willow trees in the mist in spring, while Ying Isle is popular for its cherry blossom; Liang Isle is noted for its chrysanthemums in autumn; Cui Isle wins fame for its varieties of trees and quietness; Ling Isle attracts people for its purple and golden clouds. The islets are covered by flowers, grass and trees, and connected by dykes and bridges.