Hwanseongul, the largest limestone cave in Asia, is located at Samcheok, and the massive size of the cavern overwhelms visitors. Also, Gossi and Yongyeon Caves provide the opportunities to explore a different view of a mountain that can’t be seen from the outside, since they penetrate into the middle of a big mountain. It is said that cave exploration is similar to time travel, or stepping into another dimension. Thus, visiting Cheongok Natural Cave presents a mysterious experience where the present seems to meet the history of 400~500 million years ago.