A glowing treasure awaits within the heart of these caves. Explorers willing to wade through waist-deep water and trudge through the mud in utter blackness will reach a cavern twinkling with the soft blue light of glowworms.

The Waipu Caves on New Zealand’s North Island are a great (free!) alternative to the famous Waitomo Glowworm Caves, which are rather expensive and can get really busy. This off-the-beaten-track option is unregulated and unguided, giving the whole adventure a more rugged feel.

Venture through the first chamber to gaze in awe at the stalactites and stalagmites. Once your eyes have adjusted, be sure to scan the dank chamber to search for any animal bones or invertebrate fossils hiding in plain sight within the darkness.

This first, roomy cave is only the start of the adventure. You then must follow the stream through the second chamber and into the third, clambering up slick mud banks along the way. Only there, once you’ve descended deep into the belly of the cave passage, will you find the galaxy of glowworms dangling from the ceiling.