Ключевые слова: abyss, adventure, cave, caver, cavern, chasm, dark, deep, earth, exploration, explore, finn, formation, geo, geology, hall, hole, interior, limestone, mark, mine, mystery, nguom ngao, passage, rock, scary, speleology, spelunk, spelunker, spelunking, stone, subterranean, terra, time, tourism, travel, tunnel, under, underground, vietnam,