Nanhu Island lies southeast of Kunming Lake opposite Longevity Hill. When Emperor Qianlong (1711-1799) enlarged Kunming Lake, he ordered workers to save the temples and buildings but toexcavate the earth around them, thus creating Nanhu Island. Together with other two islands in Kunming Lake, Nanhu Island symbolizes the legendary 'three fairy islands on the ocean'. Chinese people have long believed that there are several fairy islands floating on the ocean with celestial halls, like paradise. With an area of about 1 hectare (2.47 acres), it is the largest island in the Summer Palace.

Kunming Lake was customarily divided into South Lake and West Lake. Nanhu Island was named the 'South Lake Island' because of its location in southern Kunming Lake. The island is banked with carved stone-stripes and surrounded by blue and white stones. The southeast shore of the island is connected to the East Causeway of Kunming Lake by the Seventeen-Arch Bridge. There are also ferry ships from the island to the southeast and northwest shores of the lake. Rockeries and trees comprise the northern part of the island, and the south is mainly highlighted with structures. On the island stand Hanxu (Modesty) Hall, Wangyan (Looking-at-the-Eaves) Pavilion, Dragon King Temple, and other structures. They combine to form an integrated architecture, which is deemed the best sight-seeing in Kunming Lake.  They echo Longevity Hill from a distance.

Guangrun Lingyu Temple (Widely-Moistening Fancy-Rain Temple) is an important building, located in the southeastern part of the island. Its name was changed several times by Emperor Qianlong and Emperor Jiaqing. Also known as the Temple of the Dragon King, the temple was built on the ruins of the Temple of Dragon God in the Ming Dynasty (1368-1644). Its function was praying for rain. The square in front of the temple gate has three archways respectively in the south, east and west. The west and east archways were declared to be dangerous and rebuilt just as they were. In front of the south archway is the south ferry dock.

Hanxu Hall is the largest individual construction on the island. It stands out on a rockery ascent with a platform under the steps in the south. Located on the northern shore of the island, it coordinates with the Tower of Buddha Incense on Longevity Hill from afar. Here Emperor Qianlong used to watch naval exercises. Here Empress Dowager Cixi enjoyed displays performed by the naval academy. Hanxu Hall boasts the best perspective view of the surrounding scenery

Nanhu Island, it is said, is like a big tortoise crawling in Kunming Lake.  Looking down on the Summer Palace, you may surprisingly find that the round island is like the shell of a tortoise. The stairs leading to the surface of the lake are very much like the legs of the tortoise. The Seventeen-Arch Bridge seems to be its stretching neck.  Kuoru Pavilion at the eastern end of the bridge is like the tortoise's head. The lifelike shape makes people wonder if it is a coincidence.

Chinese people regard the tortoise as a symbol of longevity. The Summer Palace was repaired to celebrate the Empress Cixi's 60th birthday, and (according to the introduction from the posterity of the Summer Palace's designer) this 'huge tortoise' was indeed designed to highlight Cixi's longevity. What's more, if you climb high and overlook the whole garden, you will find that the shape of Kunming Lake is similar to a peach, which in Chinese also symbolizes good health and longevity.