Ключевые слова: adventure, asia, asian, beam, biggest, cave, daylight, dream, enlightenment, expedition, explore, geology, grotto, hike, hole, hollow, journeying, largest, light, mountains, mysterious, mystical, national, natural, nature, park, phong nha, ray, rocks, shining, site, sky, son doong, spot light, stone, sun, sunlight, sunshine, tourism, touristic, travel, traveling, trekking, underground, unesco, vertical, viet nam, vietnam, vietnamese,