Ninu's Cave was discovered by local resident Joseph Rapa in 1888 while digging a well under a private house.

Ninu's Cave is not far from another underground feature, Xerri's Grotto, also discovered when a well was being dug under a private house.

Many of these formations are dry, with the same colour as the surrounding rock, but a few are semi-transparent.

[2] The cave is entered by a 4m descent down a spiral staircase, which ends in a large chamber of approximately 20m by 8m.

Ninu's Cave is illuminated by electric lights, and is open to the public all year round.