Blue Grotto

"The infamous sea cave named for the water’s blue reflection. You can visit on a boat tour, but keep in mind that it’s only accessible when weather and sea conditions permit. Private tours get priority at the Blue Grotto, but you’ll still need to pay cash to get into one of the smaller boats that takes you inside. If you rent a boat without a crew, moor at the buoys near the grotto entrance and wait for a skipper to pick you up with a rowboat. Swimming is not allowed. If you want to head directly to Anacapri from here without returning to Marina Grande first, ask the skipper to let you off at the stairs next to the grotto. There's also a free beach and paid beach clubs nearby. You can also take a bus from Anacapri and walk down the steps to reach the grotto. The bus is at a different stop, not the main one in Anacapri, and you'll need to change buses if you're coming from Capri town."

"Grotta Azzura on the island of Capri is an amazing natural phenomenon where light filters in through an underwater hole to illuminate the grotto from below. Hop aboard a rowboat and enter the cave if you dare; inside you'll get to witness glowing blue waters like you've never seen before. Access the grotto by boat or by bus -- tickets to enter are paid on arrival and are CASH ONLY. This is a popular site on Capri during the summer months but still a worthwhile trip! "

"The Blue Grotto is stunning inside! Small row boats take you through a 3-foot opening, timing it with the waves to get inside. The unearthly water inside is stunning. But wait times during the summer can be 2+ hours. Know that even if you book a boat tour to take you to the Blue Grotto, you'll have to pay an entry fee in cash. "