The humble glow worm is, in fact, a catchall term for numerous glowing creatures, from gnat larvae to fire flys to algae, that can be found all over the world. These tiny critters illuminate the night through bioluminescence, a process in which light is emitted by internal chemical reactions. Bioluminescence has evolved independently in over 90 different species, first emerging some 540 million years ago, and today, it’s still possible to observe the phenomenon firsthand…if you know where to look.
From an abandoned tunnel in Australia, whose dank, dark walls are the perfect breeding ground for fungus gnats; to coral reefs in the Maldives that come alive at night with shimmering phytoplankton, these places are full of fascinating history and natural wonders. They’re living proof that many of the earth’s most fantastic places are off the beaten path, in the nooks and crannies (literally) where many never think to explore. Glowworms settle in the nooks and crannies between stalactites.
Luke Tearle via Instagram. These caves on New Zealand’s North Island are a lesser-known alternative to the more famous (and often over-crowded) Waitomo Glowworm Caves farther south. Visitors must venture through the caves’ first chamber of stalactites and stalagmites, follow the stream through its second chamber, then slide down mud banks into the third chamber.
Only here, deep in the belly of the cavern, will you find hundreds of glowworms lighting up the damp walls. The tunnel is home to one of the largest glowworm colonies in all of New South Wales. Fran Tapia, CC BY-ND 2.0 via Flickr **Best time to go: Any time of year, but avoid after heavy rain** An Explorer's Guide to the Hidden Wonders of the United States Introducing Our Newest Book: _America Obscura_.
Available Nov 10, 2026 The Metropolitan Tunnel, built in the late 19th century, was short-lived, closing in 1915 after soot buildup made it dangerous for train crews and passengers to pass through. The tunnel wasn’t completely abandoned, however; a colony of glowworms settled in on the roof, illuminating the stale, inky air like a constellation of blue-green stars. The tunnel still floods often, and on days when the water level is particularly high, people pass through the small waterfall on pool floats or inflatable canoes, paddling into the darkness until they reach the spots where the ceiling becomes bright with hundreds of bioluminescent bugs.
Though most commonly seen along Vaadhoo Island, the plankton have occasionally been spotted off the main island of Male. Courtesy of Maldives Local Adventure In coral reefs off the Maldives, the “Sea of Stars” phenomenon occurs during late summer, when bioluminescent phytoplankton called Lingulodinium polyedrum move with the waves. This creates an incredible shimmering effect along the shoreline.
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