The Grotta Azzurra is a sea cave on Capri’s northwest coast where light enters through an underwater opening and the refraction turns the water a glowing, unearthly BLUE. The effect is NOT artificial — sunlight passes through the submerged entrance (1.3m high), hits the white sandy bottom, and the blue wavelengths are reflected back. Roman statues were found on the cave floor in 1964 — Emperor Tiberius (who ruled from Capri 27-37 AD) used this cave as a personal SWIMMING POOL. The statues of Poseidon and Triton were placed to watch him swim in the blue light. Today: you enter in a tiny rowboat, lying flat to pass under the 1.3m entrance, and the boatman sings O Sole Mio because this is Naples.
The entrance: 1.3m high — you LIE DOWN in the rowboat. The boatman times the wave swell and pulls the boat through on a chain. Inside: 60m long, 25m wide, 14m high. The water glows blue. The boatman sings. You float for 5-7 minutes. The effect is STRONGEST 12-2pm when the sun is directly overhead. Morning: blue but less intense. Afternoon: fading. Conditions: Closed when sea is rough (waves flood the entrance). Closed roughly 30-50% of days in winter, 10-20% in summer. Check before going.
From Marina Grande (Capri): Boat to grotto entrance (15 min, €15-18 return) + rowboat entry (€18 including boatman). Total cost: €33-36/person. Yes, expensive. Yes, worth it. From Naples: Ferry to Capri (50-80 min) + boat to grotto. Or direct boat tour from Naples/Sorrento (full day, €60-100). Alternative: Swim into the grotto for free (technically illegal, practically common) — wait until the last rowboat leaves (~5pm) and swim in. The guards leave. The cave is yours. Do this at your own risk. Capri →