Modra Špilja (The Blue Cave), located in a small cove of Balun on the island of Biševo. The cave was formed by the wave action of the sea, as sea water eroded the limestone rock of which the whole island of Biševo is composed. The cave itself is 24 meters long, 10–12 meters deep and up to 15 meters high, while the entrance to it measures 1.5 meters high and 2.5 meters wide.