Ключевые слова: architecture, attraction, beautiful, calcium, cave, cave system, cavern, caving, colorful, column, dark, deep, europe, formation, geologic, geology, grotto, illumination, jama, karst, limestone, mineral, mountain, natural, nature, postojna, postojna cave, postojna jama, postojnska, rock, slovenia, speleology, stalactite, stalagmite, stone, tourism, travel, underground,