Jungmun Daepo Columnar Jointsviews: 2117
주상절리 by 멍한오리 / CC BY-SA 3.0
It is a place where you can see columnar joints (when lava flows and cools down, it hardens into a hexagonal column shape).
Admission: 2000 won (checked in June 2020)
If you go without any information, you may think that it is just the sea and stones.
If you go and listen to the description of the place in the YouTube video, the feeling will be different.
Also see the blog titled 'How columnar joints are formed'. ^^