Jeju-do, Jeju island, is the largest island of Korea and its southernmost point; since 1 July 2006 it is a Special Self-Governing Province of South Korea. It has always been a special place with its own culture and language, a Korean dialect differing greatly from those of the mainland. Because it is mutually unintelligible with the Korean dialects on the mainland, it has been recognised as a distinct language, locally and by UNESCO.
Culturally too, Jeju is different from mainland Korea. This can be observed in a number of sites, like Seongeup Folk Village at the foot of Mount Halla and nearby Jeju Folk Village Museum, just outside Pyoseon on the south-east coast of the island. These "Folk villages" are open-air museums where traditional rock-walled and thatched village houses from the 1890s have been meticulously restored. One of the typical features of the old Jeju villages are the Harubang (stone grandfather) statues, placed outside gates for protection against evil spirits. Traditionally, the phallic shaped Tol-Harubang, also once called "Beoksumeori", are gods offering both protection and fertility.
Jeju is a volcanic island, although dormant, but 360 "parasitic cones" (secondary volcanoes) have been found; the Sangumburi crater, the second largest, about 650 metres wide, 100 metres deep, and 2,070 metres in circumference, in the centre of eastern Jeju, can be easily visited. Manjanggul, the world's longest system of lava-tubes is situated in the north east of the island, These were formed by flowing lava which once moved beneath its hardened surface; when the volcanic eruption had ceased and the lava flow drained away, it left a long, cave-like channel, 13.4 kilometres long, with a height from 2 to 30 metres and a width of 2 to 23 metres. Part of it is illuminated and can be walked for a considerable distance.