Ключевые слова: abstract, ancient, black, blue, bulgaria, bulgarian, cave, cavern, caving, dark, deep, excursion, exploration, formation, geologic, geological, geology, ground, illustration, infinity, inside, interior, landscape, light, limestone, mountain, natural, nature, range, rhodope, rhodopes, rocky, skirt, snejanka, snezhanka, speleology, stalactites, stalagmite, stalagmites, stone, texture, tourism, travel, tunnel, underground,