Mt. Sangbangsan is a unique bell-shaped lava dome that resulted from very viscous lava 800,000 years ago. The lava dome is composed of columnar-jointed trachyte lava which is light gray in color. Sanbangsan is located in the southwestern margin of Jeju Island, rising 395 m above sea level. Vertical columnar joints, about 2 m in width and more than 100 m in heigh, are well exposed on the southern cliff wall of the lava dome. Beneath the jointed lava occurs a thick layer of volcanic breccia (a rock which is composed of rounded fragments of older rocks) composed of angular fragments of trachyte lava. The breccia suggests that the dome experienced explosive eruptions or dome collapse during its growth due to build-up of gas pressure. The dome-forming lava and breccia overlies the basaltic tuff of Yongmeori, the oldest rock formation on Jeju Island. A roadcut between the lava dome and Yongmeori clearly shows the relationship between these two rock formations. Sangbanggulsa is a temple built within a cave in the southwest of Mt. Sangbangsan, which is at an altitude of 200 m. It measures 10 m long, 5 m high, and 5 m wide. There are no manmade temple buildings due to its natural cave location. According to the documents, it was a place where Priest Hyeil practiced Buddhist meditation and entered nirvana in the Goryeo period. The stone statue of Buddha placed at the time was taken by Japanese people during the Japanese colonial period. A seated stone statue of Buddha was re-enshrined around 1960. Three contemporary temple buildings were constructed at the entrance around 1962. One can witness sunrise over the Yongmeori Cliff, Hyeongjaeseom island, Gapado island, and Marado island along with old pine trees outside the cave. The interior of the cave is surrounded by rock walls and crystal clear water drops fall from the rock ceiling. The water is said to represent the tears of love shed by the goddess Sanbangduk who protects the rock walls of Sanbangsan.