Introduction to the hole: Located in the northeast of BOHON Island, it is a ring-shaped stone island. In the center is a green and calm seawater lake, with a cave leading to the sea outside the island. The length of this cave is 60 meters. When the tide rises and falls, the height of the cave is about 2.5 to 4 meters. The entrance of the cave is in the shape of a bow. When visiting, tourists have to take a boat in.