Lava bridges are found in the Utsanjeongul Cave, part of the Volcanic Caves of the Upper Geomunoreum Lava Tube System, Natural Monument No. 552.
The Volcanic Caves of the Upper Geomunoreum Lava Tube System on Jeju Island -- the lava tubes Utsanjeongul, Bukoreumgul and Daerimgul -- have been officially declared Natural Monument No. 552.
The three caves are located in Deokcheon-ri in Gujwa-eup on Jeju-si City. A wide range of cave formations and ecosystems are preserved inside the lava tubes.
The lava tubes generally stretch from the northeast to the southwest. The length of Utsanjeongul is approximately 2,385 meters, Bukoreumgul 221 meters and Daerimgul 173 meters. Cave formations such as lava bridges, lava shelves and cave popcorns are spotted in the tubes, too. Also, rare cave creatures, such as the Hanguknongbal geomi spider (한국농발거미), Sinopoda koreana, and the Jejugulagi geomi spider (제주굴아기거미), Nesticella quelpartensis, can be found living inside the natural monument.
The entrance to the Daerimgul Lava Tube is located in the ceiling of the cave.
The Utsanjeongul Lava Tube lies between Bengdwigul and Bukoreumgul, the caves formed from the lava that leaked out of the Geomunoreum Volcanic Cone. Bengdwigul, a labyrinthine cave, is a UNESCO World Heritage site. Although the end of Utsanjeongul has collapsed and blocked the passage, the cave is connected to Bukoreumgul. The cave is decorated with lava bridges and lava shelves. It's noticeable for its plaster cave popcorns, some of the only ones found in Korea.
Finally, be sure to check out Bukoreumgul. Because its passage is broken down, Bukoreumgul has multiple lava bridges that make for a wonderful spelunking trip.