It refers to a short stretch of mountain path about 3 Chinese li long which is fairly level even downward between Middle Heavenly Gate and Cloud Stepping Bridge. When tourists arrive here, they have gone through a long and cliffy flight of stone stairs, and they are too exhausted to take even one more stair. Then a level path without any stairs appears. This will supply them with vigor and confidence, and put them in a good mood. That's the name Cheerful Three Li comes from.