Originally called Dapi and commonly known as “Dapo Lake”, Longtan was among the “Lanyang Twelve Scenic Wonders” due to its fascinating scenery. It is situated in the Longtan Village of Jiaosi Township covering a total ground area of about 20 hectares and that made it the biggest of the five major lakes in Yilan. Strolling along the circular trail around the lake, the tourists will enjoy the beauty of nature such as colorful butterflies dancing around the green trees and water birds flying over the peaceful lake.

There are also several temples around the lake. Located on the mid-slope of the mountain, Longtan Temple, overlooking the lake from high above, provides serenity for its worshipers to practice Taoist rules. Huangti Temple that worships Huang-ti (the Yellow Emperor) is another renowned temple near Longtan Lake.