Ключевые слова: beautiful, beauty, bulgaria, cave, color, colorful, colour, colourful, deep, different, extreme, flowstones, geology, illuminated, inside, inside of, light, lighted, limestone, material, mountain, national landmark, natural column, nature, onyx, rock, semiprecious, stalactites, stalagmites, stone, stones, structure, tourism, travel, underground, venetsa, venetsa cave, vivid,