Cala di Sa 'Olta Niedda, Santa Caterina di Pittinuri, Sardinia, Italy. This huge limestone rock in the shape of a wrench and with a diameter of about 100 meters is undoubtedly one of the most incredible natural creations I have ever seen. Furthermore, the breaking of the waves on it has literally smoothed it, giving it a rounded shape like a sausage, which makes it truly unique. In the photo you can see the Spanish tower.