The Nature Reserve is formed by three islands: Pantaleu, Mitjana and Sa Dragonera; besides it has an important Area of Marine Influence that contains part of the resources that uses the fauna of the littoral of the park. As a whole 908 ha, of that 274 form the surface of the nature reserve. It is separated of Majorca by a small channel (800 m) not much deep with sandy covered by Posidonia oceanica, a real submerged forest, many marine species' refuge.