On my list:

The Loyalty Islands are devoid of rivers. Rainwater penetrates the coral reef until it meets the seawater where, due to its lower density, it forms a deep layer of fresh water, this underground circulation of rainwater is at the origin of the vast network of caves and avens. In Lio, halfway between Tenane and La Roche, a safety barrier appears at the side of the road signalling the location of the Bone hole. A short narrow path quickly leads to a circular chasm 30 m in diameter and 40 m deep, where like vines, the banyan roots drop along the walls to draw water from the bottom of the hole. Truly dizzying!