You can only get to the glowworm cave as part of a booked tour.
First you take a 30-minute catamaran ride across Lake Te Anau. A short path through the rainforest leads to the cave entrance. Inside you walk about 200m on a metal walkway over a roaring underground river. The noise is so loud that you can hardly hear your own voice. Then you board a small boat and travel in total darkness and silence to the cave with the most glowworms.
On the way out we were able to see the eel that lives in the cave.
At the castle there is also a lecture about the life of these animals.
Photography is not allowed in the cave.