Skylit shore

Even amidst the many spectacular cliffs and sea caves that line southern Portugal's Algarve coast, Benagil Cave is an eye-catcher. The cave was formed about 20 million years ago from the pounding waves that sweep in from the Atlantic. Rainfall has caused softer segments of limestone to erode, creating a giant hole in the cave's roof, which is what we're looking down through in our photo. The eye-shaped opening allows sunlight to stream into the cave, illuminating the golden beach and azure waters within its walls.