Passing through Longshandong again is a long cave in Gulangyu Island, about 500 meters. One end of the cave is not far from Sanqiutian Wharf, and the other end exit is to Neicuoao Road, which is a fast passage between Gulangyu East and Neicuoao. The height of the cave is quite high, the winter is warm and the summer is cool, and you can feel the history of civil air defense in the past.