The Island of Mal di Ventre is what has remained of a large granite outcrop which edged the whole western coast of Sardinia in very ancient times.
It has a surface of about 80 hectares and is about 5 nautical miles from the coast; it maximum height on the sea level is about 18m.
The weathering of its rocks feeds the sands of the quartziferous beaches of the Sinis. The landscape is characterized by the intrusive granite rocks with particular shapes resulting from the erosive action of the often exceptional forces of nature which sometimes create shapes which have been transformed by the popular imagination into persons, things, or animals.