A series of sea caves along Malta’s rugged southern coast, the Blue Grotto gets its name from the extraordinary phosphorescent blue light that illuminates the water when morning sunlight reflects off the white sandy seabed and through the underwater caverns. Small traditional boats called luzzu carry visitors through a chain of six caves, each revealing different shimmering hues of blue, green, and violet as the light plays through the crystal-clear Mediterranean waters. The largest cavern is big enough for boats to turn around inside, and the towering natural rock arch at the entrance frames postcard-perfect views of the open sea. Above the caves, a panoramic viewpoint offers stunning clifftop vistas of the entire coastline.

Pro tip: Arrive early in the morning, ideally by 9 AM, for the most intense blue colors and calmest seas — afternoon winds can sometimes cancel boat trips entirely.