The Te Anau Glowworm Caves lie on the western shore of Lake Te Anau, accessible only by boat from town — a 20-minute crossing. Real Journeys runs guided tours that take visitors deep into the cave system on foot and then by small underground boat beneath a ceiling hung with thousands of glowworms (Arachnocampa luminosa). The effect in the darkness is genuinely spectacular: a dense blue-green galaxy overhead, reflected in the still water.
Tours depart in the afternoon and evening and last about 2.5 hours including the boat crossing. Booking ahead is recommended in summer. Photography inside the caves is not allowed — cameras with flash could harm the glowworms and the darkness makes photos useless anyway. The evening tours are worth choosing for the atmosphere of the crossing back across the lake in the dark.