Longtan Mountain is named after a beautiful pool called Longtan at the foot of the northwest corner mountain. Longtan is about 53 meters long, 26 meters wide and 9 meters deep. Stacking stones is a dike, and the water is clear to the bottom. Whenever the bright moon hangs high and the reflection ripples in the middle of the lake, it is the "Longtan printing the moon" that makes people linger.
Longtan, also known as the water dungeon, is the reservoir of the ancient castle in northern Xinjiang of Koguryo. According to legend, in ancient times, a dragon was locked at the bottom of the pool and chained to a tree by the pool. When someone pulls the chain, the clouds immediately change color and the water in the pool churns. There is an ancient birch tree in the southeast of Tantan, which is 30 meters high. They can't hold each other's arms together, and they are dignified and straight. Qinggan Dilong swam north here, named "Holy Tree". There are ancient buildings such as Longwang Temple, Guandi Temple and Longfeng Temple nearby for sightseeing.
There is an ancient city of Koguryo at the top of Longtan Mountain. The wall is ten meters high, the base is ten meters wide and the circumference is two thousand four hundred meters. This is an ancient military castle. Condescending, there is a tendency of "one person's defense is above ten thousand people". There is a platform in every corner of the ancient city, and the south platform has the highest terrain, commonly known as Nantianmen. You can see a panoramic view of the whole city of Jilin.