Sangumburi Crater
More than 6,500 feet in circumference and 420 feet deep, Sangumburi is not only one of the largest of Jeju's 360 volcanic craters, but it's also a rare "maar"—that is, it was formed when groundwater came into contact with magma, causing an explosion. The crater functions as a nature preserve, hosting more than 400 species of trees and plants and populations of deer and other animals. The crater is particularly spectacular in autumn, when its flanks are covered in shimmering silvergrass. Its rim offers fine views of Hallasan as well. The crater is an easy five-minute walk from the park gate.
