The Waipu Caves Scenic Reserve in New Zealand is a hidden gem for spotting glow worms. Bring a torch and wear shoes and pants that can get wet, as you'll need to walk through small streams to reach the main cave.
There are two cave rooms to explore: the main one after crossing a couple of streams, and a secondary one that requires crouching and walking along a knee-deep stream. Be cautious about exploring the second cave room, especially if the water is high.
Tip: The quieter and darker it is, the more glow worms you'll see so turn off your torches when looking for them.