The Waitomo Glowworm Cave is New Zealand's most famous underground experience and one of the most visited natural attractions in the country. A guided tour leads through several chambers of limestone formations before culminating in the grotto — a large underground lake where you board a flat-bottomed boat and float in darkness beneath a ceiling studded with thousands of glowing blue-green lights. It is genuinely magical.
The cave itself has significant geological interest: stalactites, stalagmites, and cave coral formations built over hundreds of thousands of years. The tour takes about 45 minutes and runs continuously throughout the day. Booking in advance is essential in peak season (December through February), when queues can be long and tour times sell out. The cave is operated by Waitomo Caves, and combined tickets with other area activities are available.