The Cíes Islands are truly a natural paradise of exceptional ecological interest. The craggy granitic rock hills and cliffs of these three islands were once well known as a hideout for pirates. The western sides of the islands share nearly vertical cliffs and numerous sea caves, both formed by erosion from wave action generated by Atlantic squalls as they pass over the islands. The more sheltered eastern side is protected from the salt spray of Atlantic winds and has formed beaches and dunes carpeted with brushy vegetation. The area is now a nature reserve and home to over 15,000 nesting seabirds, most of them Yellow-legged Gulls. The water around the islands is exceptionally clear and cool, and the islands are a favorite recreational spot for the local people.