Introduction to Nanda Ridge: The terrain of Nanda Ridge on Dazhou Island is steep and there is no way to climb it. From November to March of the following year, groups of swiftlets fly to Dazhou Island to nest for the winter. The more than 100 cliff caves on the island have become natural resorts for swiftlets to build nests. The nest is glued with the saliva of swiftlets, which is the precious "Wanzhou Bird's Nest". Because it is rich in nutrients and has extremely high medicinal value, it is both a delicacy and a valuable medicinal material. Therefore, it enjoys the reputation of "Oriental Treasure" and "Rare and Famous Medicine". It has been a tribute from the late Ming Dynasty to the early Qing Dynasty.