The Blue Grotto is the most famous sea cave in the Mediterranean and one of the most visited natural sights in Italy. The effect that gives it its name is created by sunlight entering through a wide underwater opening and refracting upward through the water — the interior glows a luminous, almost neon blue that photographs cannot fully capture. The cave is about 54 metres long and 15 metres wide.
You reach it by boat from Marina Grande, then transfer to a small rowboat at the entrance and lie flat while the boatman pulls you inside on a chain at the exact moment a wave lowers the water level enough to clear the entrance arch. The visit inside is short — five to ten minutes — and the experience is genuine despite the organised-tour atmosphere around it. Go in the morning when the light inside is strongest; after midday it fades. Rough seas close the grotto on many days, so check conditions before making the trip.