Ключевые слова: background, calcium, cardona, catalonia, cave, cavern, corridor, crystal, deep, depth, digging, disuse, drill, dripping, europe, gallery, geology, grot, grotto, history, industry, inside, mine, mineral, mining, natural, obsolete, old, potash, rock, saline, salt, salty, solid, spain, speleology, stalactite, stalagmite, stone, subterranean, texture, tunnel, underground, wall, water, wet,