Changkkom

Manjanggul Lava Tube

A lava tube about 7.4 km long whose main passage runs 18 m wide and 23 m high. Roof collapses left three entrances; visitors may use only the second, and may walk 1 km in from it. At the end of that kilometre stands a lava column about 7.6 m high, said to be the largest known anywhere, and that column is also where you turn round. The operator files this cave as partly open — the other caves inscribed with it are closed to the public altogether.

Geomunoreum

The volcanic cone that made the caves on this side of the island: lava from here ran about 14 km to the coast and left the Geomunoreum Lava Tube System behind it. In front of the cone a collapse trench runs about 2 km long, 80 to 150 m wide and 15 to 30 m deep, thought to have formed where cave roofs fell in. There are three routes of different lengths, two of which may only be walked with a guide. Eleven departures a day, fifty people each, and booking closes at 17:00 the day before.

Secret Forest

A walk through cedar west of Andol Oreum, with tickets sold from a mint-coloured truck at the entrance. The unpaved loop takes about half an hour and has eight marked spots to photograph, with a stand of hinoki cypress partway round. Closures are posted on the operator's Instagram rather than following a fixed calendar, which is worth checking before driving out here.

Bijarim Forest

Two loops split at a crossroads inside the wood. Course A is about 2.2 km of level volcanic-cinder path, 40 minutes to an hour, and takes a pushchair or wheelchair with help on the slopes; course B includes rough stone and does not. Dogs are not admitted, which separates this from most Jeju walks.