Modra špilja, located on Biševo Island near Vis in Croatia, is a natural sea cave known for its distinctive blue illumination. Visitors typically reach the cave by organised boat or speedboat tours, where they can enter in small vessels, observe the interior light effects and surrounding rock formations, and take photographs. The site is notable for its bright blue glow created when sunlight reflects through an underwater opening, as well as its clear waters that reveal the rocky seabed, making it one of the more visited natural attractions along the Adriatic coast.