Nisida is a volcanic islet of the Flegrean Islands archipelago, in southern Italy. It lies at a very short distance from Cape Posillipo, southwest of Naples; it is connected to the mainland by a camera-enforced 1km-long pedestrian zone. The islet is almost circular, with a flooded crater forming the bay of Porto Paone on the southwest coast. It has a diameter of about 0.5 kilometres and a highest altitude of 105 metres.