Ключевые слова: adventure, adventure tourism, cave, crystals, curiosity, darkness, dramatic light, earth, environment, european tourism, exploration, formations, geology, guided tour, hidden places, historic site, interior, landscape, lights, mira de aire, mystic, natural beauty, natural wonder, nature, portugal, rock formations, rocks, scenery, shadows, spectacle, stalactites, stalagmites, stone, subterranean, texture, tourism, travel, underground, underground cavern, water reflections,