The eastern tip of Jeju is where the island's volcanic origins are most obvious. Seongsan Ilchulbong, the Sunrise Peak, rises straight from the sea here, a huge bowl-shaped tuff cone with steep green walls and a crater wide enough to hold a village. It formed when rising magma met seawater a few thousand years ago and blew itself apart into layers of ash, and the sea has been cutting at its sides ever since. It is part of the UNESCO World Heritage site that covers Jeju's volcanoes and lava tubes, and the climb to the rim, steep and stepped, takes about twenty minutes.
This corner is also the heartland of the haenyeo, the women divers who have harvested shellfish, sea urchins and seaweed from these waters for generations, holding their breath and diving in all seasons. Their culture is recognised by UNESCO, and at Seongsan you can sometimes watch older divers come ashore with their catch in nets, still in wetsuits, and buy sea urchin or abalone from them. The divers are fewer and older every year, which makes it worth seeing while you can.
The coastal road around here is flat and windy, in both senses: it follows the shoreline in small bends past black basalt rocks, fishing harbours and low stone walls built from the volcanic stone that is everywhere on Jeju. The wind can be strong enough to push a bike sideways, especially in winter, when cold air comes down from the north. Spring brings fields of yellow rapeseed flowers around Seongsan, and early mornings are the best time, before the tour buses arrive and while the low sun lights up the cone.
From the harbour at Seongsan a short ferry runs to Udo, a small island with white sand, peanut ice cream and a quiet coastal road, and many visitors take scooters or small bikes across. The town around the harbour has fuel, convenience stores and many small restaurants serving seafood, as well as Jeju's black pork, a local breed grilled at the table. Jeju City is about forty kilometres away, so fill up here if you are continuing south along the coast towards Seogwipo, where the next large services are.