The gorgeous Cala Sabina is located on the island of Asinara, a former sanatorium then high security prison and currently a highly protected national park. Nobody but the park rangers and a bunch of wild boars, donkeys and foxes live on the island, which can be explored by bike or hiking. Cala Sabina is one of the busiest beaches, and when it gets crowded it can count a whopping 20 people around.