An Algar is a natural cavity formed by wind and water erosion. This one specifically is called Algar of Benagil. There is a large natural opening at the top that allows the entry of sunlight and is accessible only by sea. On this trip we entered the cave by the most unlikely place, the opening in the roof. It is an unusual landscape of rare beauty that resembles a hidden cathedral under the rocks, where we only hear the singing of the sea and see the spotlight coming from the huge opening in the ceiling, giving life to the beach which is hidden inside the cave.