Hyeopjaegul & Ssangnyonggul Cave
Natural Monument No.236 of South Korea
Hyeopjaegul and Ssangnyonggul caves were formed by an eruption of Mt. Halla many years ago and considered as a unique place of history by geologists. Fossilized seashells and abalone shells were found which lead many to believe that the caves were below sea-level at the time of formation. In the area, over 20 caves are connected in a single system spanning over 17,000 meters which is the longest in the world, and only 500 meter portion of Hyeopjaegul and Ssangnyonggul caves are currently open to public. The temperature inside of the caves is 12~18 degrees Celsius all year around so visitors can enjoy cool temperature in summer and keep warm in winter.