Hyeopjaegul Lava Tube (Hallim Park) (협재굴(한림공원))

Hyeopjaegul Lava Tube (Hallim Park) and Ssangyonggul Cave are representative lava tubes of Jeju Island located within Hallim Park. Formed during the volcanic eruptions of Hallasan approximately 2.5 million years ago, they are designated as Natural Monument No. 236. The internal temperature of the caves remains steady at 17–18°C throughout the year, and despite being lava tubes, they feature the formation of stalagmites and stalactites, creating a mystical landscape.