The grotto is a massive flooded cave with an opening into the sea. Reflected sunlight makes the cave appear to be lit from inside with an eerie bright blue glow.

 Small boats cluster near the entrance to take tourists into the cave through an opening that is barely a meter high - you may have to lie on the floor of the boat to get through, and when the sea is rough, it is impossible to enter. 

Romans thought it the home of sea nymphs, but since the 19th century, it has been Capri's major tourist attraction. To access the Blue Grotto, take a boat from Marina Grande or a bus from Anacapri or by the Via Pagliaro (three kilometers) from Anacapri.