Introduction to natural woodland: Outside Yanzi Cave, there are ancient and famous trees with luxuriant branches among the cliffs. The natural woodland covers an area of ​​more than 30,000 square meters, in which dozens of species of birds inhabit. There are hundreds of thousands of white-rumped swifts nesting on the rock walls inside and outside the cave, hence the name Swallow Cave. Every spring and summer, flocks of swallows fly in like thousands of arrows. Hundreds of thousands of swallows appear and disappear, and the sound of whispering is endless. The sound of swallows and the sound of water resonate in the cave, forming a cave symphony that shakes the valley. .