2 Best Sights in Hallasan National Park, Jeju-do

Jeju's dominant topographical feature is Hallasan, an extinct shield volcano that looms 1,950 meters (6,397 feet) over the island. The mountain's lower slopes are covered in dense woods, fields, pastures, and citrus groves that give way to grassy meadows, azalea fields, and forests of dead yew trees at higher elevations. More than 360 parasitic cones cover the volcano's flanks. There are seven hiking trails up the mountain, though the two most popular—the Seongpanak and Gwaneumsa trails—now require reservations. Both take about 10 hours, and while the hike to the crater at the peak can be a slog, no technical climbing is required and the views over the island are well worth the effort. Beware of the strong winds and sudden change in temperature as altitude increases. Hallasan has camping sites, parking, a visitors center, and bathrooms.

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.