Gwaneumdo is located 5km northeast from Jeodong port and its total area is 71,450㎡. The uninhabited islet is 106m high and has a circumference of 800m. It is the third largest dependent islet of Ulleung-do following Dokdo and Jukdo. The two 14m high caves on the northeastern part of the island are called Gwaneum Ssanggul (Gwaneum Cave). When the first settlement policy began, a fisherman (Kim of Wolseong) from Gyeongju was caught in a storm and happened to find the island. When he made fire to stay overnight, herds of ggaksae brids came to the fire. He survived by eating the birds. Since then, the island is also referred as ‘ggaksae bird island’. Some say that pirates would hide their ship in Gwaneum Ssangul and plunder ships passing by. A legend has it that drinking water dripping off the ceiling of the cave gives long life. Gwaneumdo, formed of lava flows, was once attached to Ullueng-do. Later, the islet was separated to its present formation due to differential erosion. The upper surface of the islet is covered with pumice. The substructure of Gwaneumdo has well-developed columnar joints. Radial joints are also found around Gwaneumdo. Columnar joints and horizontal joints of the islet’s cliffs are easily eroded by waves. Gwanum Ssangul was formed after the rock formations along the joints collapsed.