Nanhu Island lies southeast of Kunming Lake opposite Longevity Hill. With an area of about 1 hectare (2.47 acres), it is the largest island in the Summer Palace. When Emperor Qianlong (1711-1799) enlarged Kunming Lake, he ordered workers to save the temples and buildings but to excavate the earth; thus creating Nanhu Island.

On the island are Hanxu (Modesty) Hall, Wangyan (Looking-at-the-Eaves) Pavilion, Dragon King Temple, and other structures. Hanxu Hall is the major construction on the island; Wangyan Pavilion was the site from which to inspect navy drills; and the Dragon King Temple, which changed its name to "Guangrun Lingyu Temple" (Widely-Moistening Fancy-Rain Temple), was employed to pray for rain.

The island is banked with carved stone-stripes and surrounded by blue and white stones. Visitors can reach the island through the Seventeen-Arch Bridge.

An interesting saying goes that there is a big tortoise crawling in Kunming Lake. It is Nanhu Island. Overlook 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 crawls of the tortoise. The Seventeen-Arch Bridge seems to be its stretching neck. Kuoru Pavilion in the eastern end of the bridge is associated with the tortoise's head. The lifelike shape makes people can't help asking whether it is a coincidence.

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