Introduction to Haiwu Grand Hall: Zhanggong Cave is divided into two caves, front and rear. It is a large hall with many caves. There are holes in the caves and the caves are connected. The whole cave covers an area of more than 3,000 square meters, and the tour length is about 1,000 meters. There are Sea House Plaza and the magnificent Neptune Hall in the cave. It is often shrouded in clouds and mist, and visitors feel like they are in an underwater palace. Zhanggong Cave has a characteristic called big holes within holes, middle holes within small holes, and small holes within holes. They are holes within holes, holes connected to holes, and holes within holes. The holes are connected, but the holes are different. According to statistics , Zhanggong Cave has 72 holes, large and small.