Dian Lake, also known as Dianchi Lake, is a rift lake southwest of Kunming, China. It was known by multiple names in ancient times, including the Marsh of Southern Yunnan, Kunming Lake, and the Pond of Kunming. The surface of Dian Lake is at an altitude of 1,886.3 meters above sea level. It has a north-south length of 40.5 kilometers and east-west length of 7.3 kilometers, an average depth of 4.1 meters (5.87 meters at its deepest), covering an area of 298 square kilometers. The bow-shaped lake is a natural body of water containing 1.2 billion cubic meters of water. Sea Dyke lies in the northern part of the lake and divides the lake into two sections. The section outside the dyke is the Outer Sea with a depth of three to five meters. The section inside has a depth of one to two meters and is known as Grass Sea, West Lake, Wave-Accumulating Lake, or Green Grass Lake. The amount of outflowing water through the Haikou River, the only river connected to the lake, is half of a billion cubic meters. The Haikou River is also called the Tanglang (Mantis) River because of the shape of its shoreline. The river produces plentiful hydropower. In 1910, the first hydropower station was built at Shilong near Haikou. Passenger transport service is available between Kunming and Haikou.
Dian Lake teems with carp, crucian, snakehead fish, gold-lined fish (Nemipterus virgatus), and other creatures. The lake area is a major national scenic attraction. By the lake, tourists can visit Grand View Tower and West Mountain, which are two nationally-famous scenic spots.