Ключевые слова: abandoned, catacomb, cave, cavern, coal, construction, copper, corridor, dark, deep, dig, dirt, dirty, dungeon, engineering, entrance, equipment, excavate, geology, historical, history, hole, industrial, industry, inside, interior, iron, light, limestone, machine, metal, mine, miner, mineral, minerals, mining, mountain, mystery, passage, railway, rock, stone, technology, tunnel, tunneling, underground, underpass, way, work,