Just a scenic 20-minute walk from the heart of Cascais, you'll find this incredible chasm carved into the cliffs by the sheer force of the Atlantic. It's a spot where you can truly feel the power of the ocean as waves crash and boom into a collapsed sea cave, creating a sound that gives the place its dramatic name. For the most spectacular show, try to visit on a stormy day or during high tide when the sea is at its most ferocious. Otherwise, a calm day offers a beautiful, rugged coastal scene perfect for watching the sunset.