With an international reputation as one a fascinating destination, the Waitomo Caves open the door to an enchanted underground world. In fact, the caves are home to millions of glowworms and I had the impression of being six feet underground beneath a starry night sky!
For the occasion, I had booked a package that included abseiling into a 35-meter deep cave, followed by cave exploration combined with canyoning and gently floating through the cave's waterways on large air tubes before completing a gentle climb back to the surface. This trip to the bottom of the caves took place under the watchful eyes of the glow worms, that covered most of the cave walls. It all went very well and the route is well-known. However, I did find it rather expensive for what it is.
In New Zealand, other, less tourist-focused caves exist, where you can also find colonies of glow worms, perhaps not in the same numbers - but the sight is no less impressive for that.