Jeju is famous for its production of citrus fruits and the island produces a number of varieties including the hybrid Hallabong, so called after Mt. Halla and Gamgyul.
Hallabong are known for their sweet flavor and are more expensive than normal mandarin oranges.
Hallabong have a distinctive bump at the top and are used to make Hallabong tea and even chocolate. Jeju's varieties of citrus fruit are a popular souvenir and are exported as far as the UK. You can purchase them in boxes from roadside vendors or in Jeju's market not far from the port area.