It is the most famous place on the island of Capri,the most spectacular and without doubt,at least during the tourist season, one of the most crowded.
Its name and beauty are due to the intense blue color of the crystal-water in this cave formed over the millenniums by the erosive action of the sea.
The cave consists of several enclosures:the largest of these, known as “Duomo Azzurro”, which is accessed through a natural opening artificially widened in Roman times and around 1830 ,covers a surface area of about 70 m lenght, 25 m in widht and 20-22 m in depth: the height of the internal vault ranges from 7 to 14 m. From this main cavity lead many corridors and passages to other underground ravines.
The light is filtered by the water which absorbs the red tones, leaving only the blue ones to pass into the cave. A second phenomenon creates the silver appearance of the objects immersed in the water: given that the index of refraction of the bubbles of air which adhere to the surface of the objects is different to that of the water, the light is allowed to egress.
It is believed that, in the Roman period, under the rule of Tiberius, the interior of the Grotta Azzurra or Blue Grotto was used as a marine nymphaeum.
There have been those who imagined the cave as the habitat of Nereidi or of Sirens or believed it to be the realm of devils who bewitched all who dared to enter.
Unfortunately this amazing cave is open one day out of four about 90 days a year, it depends on the tides and of course also if the sea is little rough is closed because the entrance of this magical cave is about 1 meter high.