The Bue Marino Grotto near Cala Gonone can be accessed only by boat and in Summer a daily transport service is available from the harbour. The Grotto is famous for being one of the last habitats of the monk seal, although today is very rare to see it, and for the height of some of the caves. There are traces that show the presence of man since ancient times as early as the Neolithic Age, when it was probably used as a place of worship