Travel deep dive
Jeju: The Island That Is a Volcano
Jeju is usually introduced as Korea's holiday island, which is true and tells you almost nothing. The more useful description is geological: Jeju is a shield volcano that grew from the seabed until it broke the surface, and Hallasan, the peak at its centre, is not a mountain standing on the island but the summit of the island itself. Everything else here — the caves, the cones, the walls, the absence of rivers, even the diving tradition — follows from that.
Updated 2026-08-15
The island is the volcano
A shield volcano is built by runny lava flowing long distances rather than by explosive eruptions piling material steeply, which produces a broad, gently sloping dome instead of a classic cone. Jeju is one, and it is the whole island: the land tilts upward from every stretch of coast toward Hallasan at the centre, South Korea's highest point at just under two thousand metres. Drive inland from anywhere on the ring road and you are climbing the volcano.
This is also why Jeju holds an unusual distinction — it carries all three of UNESCO's major natural designations, as a Biosphere Reserve, a World Heritage site and a Global Geopark. Very few places anywhere hold the full set, and it reflects the fact that the island is not one remarkable feature but a complete and unusually legible volcanic system that you can walk around in a few days.
The oreum: three hundred smaller cones
Scattered across Hallasan's flanks are around three hundred and sixty oreum — small secondary cones formed by eruptions from side vents rather than the main summit. They are the defining unit of the Jeju landscape and the thing photographs never quite convey: rounded grassy hills, often with a shallow crater on top, standing alone or in loose chains across pasture and farmland.
Most are climbable in twenty minutes to an hour, and this is the single most rewarding low-effort thing to do on the island. From the top of almost any of them you see the same composition — other oreum receding into haze in one direction, the sea in another, and Hallasan above it all — which makes the island's structure suddenly obvious in a way no map achieves. Locals have favourites, they are free, and they are almost never crowded.
Sunrise Peak and the lava tubes
Seongsan Ilchulbong, on the eastern coast, is the island's most photographed single feature and a different kind of volcano again. It formed where rising magma met seawater, and the resulting steam explosions built a broad bowl of compacted ash rather than a lava cone — which is why it is a crater rim you climb into rather than a peak you climb over. The name means sunrise peak, and the climb is genuinely a sunrise activity for good reason.
Underground, the same eruptions left lava tubes: tunnels formed when the surface of a lava flow cooled and crusted over while molten rock kept running beneath it and eventually drained away. Manjanggul is the one open to visitors, and a long section of it can be walked — a cold, dark, high-ceilinged passage with lava terraces along the walls marking old flow levels and, at the far end, a lava column formed where molten rock poured through from a tube above. Bring a jacket; it is cold underground regardless of the season.
Why there are no rivers, and what that did to the island
Basalt is porous, and Jeju is made of it. Rain does not run off the island so much as vanish into it, travelling underground and emerging at spring lines near the coast, which is why Jeju has almost no permanent surface rivers despite substantial rainfall. Traditional villages sit where the water reappears rather than where a river runs, and the streambeds you cross inland are dry most of the year.
That single hydrological fact shaped the island's economy for centuries. Without reliable surface water, wet-rice agriculture — the foundation of the Korean mainland's food system — was largely impossible here, and Jeju farmed dry crops instead: millet, barley, buckwheat, and much later the tangerines that now scent the coastal roads in autumn. The fields are divided by low dry-stone walls built from the volcanic rock cleared off the land, thousands of kilometres of them, stacked loosely so the island's severe wind blows through rather than against them. The same black basalt is carved into the harubang, the broad-faced stone grandfathers that stand at village entrances.
The haenyeo: when the sea is the field
If the land could not be farmed in the usual way, the sea could be harvested, and on Jeju that work became women's work. The haenyeo dive without breathing apparatus to gather abalone, sea urchin, octopus and seaweed, holding their breath for a minute or more at depth, working through the cold months in a rhythm learned over decades. The practice is recognised by UNESCO as intangible cultural heritage, and it produced something unusual in Korean social history: households where the principal earner was a woman, and a diving community with its own hierarchy, rules and safety customs.
The tradition is genuinely ageing — most active divers are now elderly, and the numbers have fallen sharply from their mid-century peak — which makes the encounter more valuable and more delicate. Scheduled demonstrations take place at some coastal sites and there is a museum devoted to the practice, but the honest version is simpler: at the right small harbours you can watch divers come ashore and buy what they have just brought up, eaten within sight of the water it came from. Watch, buy, and let them work.
Climbing Hallasan and walking the Olle trails
Hallasan can be climbed in a long day, and only two of its routes reach the crater rim at the summit; the others stop lower on the mountain. The mountain is managed with firm turnaround times, so the practical constraint is not fitness but the clock — you must be past checkpoints by set hours or you will be turned back, which means starting very early. The summit sits in cloud a great deal of the time, and the walk up through changing forest belts is the reliable pleasure rather than the view from the top.
At sea level, the Jeju Olle Trail is the alternative and, for most visitors, the better one. It is a waymarked coastal walking network running most of the way around the island, divided into some twenty-odd numbered routes of a day or less each, threading between fishing villages, oreum, beaches and farmland. You can walk one route as a day out or chain several across a week, and because each begins and ends somewhere with buses, it works without a car. The name comes from the Jeju word for the narrow lane connecting a house to the road, which is exactly the register of the walking.