The Blue Grotto or Blue Cave, is a flooded sea cave located in a small bay called Balun, on the east side of the island of Biševo and about 4.5 nautical miles (8.3 km) from Komiža, in the Croatian Adriatic. It is situated in the central Dalmatian archipelago, 5 km south-west of the island of Vis. The grotto is one of the best known natural beauty spots on the Adriatic and a popular show cave because of the glowing blue light that appears at certain times of day.