Hwanseongul Cave 환선굴

"Hwanseongul Cave is the biggest lime stone cave in Korea. Its length is 6.5 km and it features fantastic stalagmites, stalactites, and about 10 lakes and waterfalls. Some spots of interest include stalactites that look like the Great Wall of China and many other uniquely shaped figures. The mercury inside of the cave keeps it at a cool 12-24℃ in the summer and 8-9℃ in the winter."