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The 12 Best Caves and Grottoes You Can Walk, Swim, or Boat Through
Going underground is the most underrated thing in travel. The best caves to visit aren't dusty geology lessons — they're glowworm galaxies, electric-blue sea grottoes, and rivers you boat down in the dark. Twelve worth descending for, on foot, by water, or both.
The best caves to visit do something the surface never can: they make you genuinely unsure if you’re awake. I’ve stood in pitch dark under a ceiling of glowworms in New Zealand and lost all sense of up. It’s the closest I’ve felt to floating in space without leaving the ground.
Underground travel gets skipped because it sounds like a school trip. It isn’t. Some of these you walk, some you swim, one or two you boat through in silence in the dark. All twelve are worth descending for.
1. Waitomo Glowworm Caves, New Zealand
The headline act. You drift in a small boat through a black grotto under a ceiling of thousands of glowworms — bioluminescent larvae that look exactly like a clear night sky pulled down to arm’s reach. The guides hush you, kill the lights, and let the boat glide. For the more adventurous, blackwater rafting tubes you through on an inner tube. Either way: unreal.
2. Grotta Azzurra (Blue Grotto), Capri, Italy
The famous one, and famously fiddly. You transfer into a tiny rowboat and lie almost flat to clear the low sea entrance — then the cave opens up and the water glows an impossible electric blue from sunlight refracting under the rock. It’s brief, it’s a bit of a circus, and it’s still worth it. Go mid-morning on a calm day; high seas close it without notice.
3. Škocjan Caves, Slovenia
Criminally underrated. A vast underground canyon with a river roaring through the bottom, crossed by a footbridge a hundred metres up in the dark. The scale is genuinely vertigo-inducing — way more dramatic than the better-known Postojna down the road. You walk this one, and your legs will know it.
4. Phong Nha & Paradise Cave, Vietnam
Central Vietnam is riddled with some of the planet’s biggest caves. Paradise Cave (Thien Duong) you walk on a boardwalk through cathedral-sized chambers of stalactites. Phong Nha itself you enter by boat down an underground river. (The truly enormous Son Doong needs a permit, a guide, and serious money — but seeing photos of it is what gets people to the region in the first place.)
5. Reed Flute Cave, Guilin, China
Theatrical in the extreme — the chambers are lit in saturated pinks, greens, and blues that reflect off still pools, which sounds gaudy and somehow works. It’s been drawing visitors for over a thousand years; there’s Tang dynasty graffiti on the walls. You walk it. Bring a sense of humor about the disco lighting.
6. Benagil Sea Cave, Algarve, Portugal
The grotto with the hole in the roof — a golden domed sea cave with a circular skylight and its own little beach inside, reachable only from the water. Kayak or SUP in (don’t take the crowded tour boats if you can paddle), and time it for early morning before the Algarve armada arrives. You can swim through the entrance on a calm day.
7. Antelope Canyon, Arizona, USA
Technically a slot canyon, not a true cave — but you walk through it, the light shafts pierce down through the narrow opening, and the wave-carved sandstone glows orange and purple. It’s roofless in places, so it’s the “barely underground” entry. Navajo-guided only, and book ahead. Midday is when the famous light beams appear in Upper Antelope.
8. Cango Caves, South Africa
In the Klein Karoo, a series of huge dripstone chambers you walk through on a guided tour. There’s a standard route and an “adventure” route that has you squeezing through genuinely tight crawls with names like the Devil’s Chimney — only do that one if you’re sure about small spaces. The main hall is staggering on its own.
9. Marble Caves (Cuevas de Mármol), Patagonia, Chile
Swirled blue-and-white marble caverns carved by 6,000 years of waves on a glacial lake, reached only by small boat. The water is an unreal turquoise and the marble walls ripple like frozen smoke. The boat noses right into the low chambers. Lago General Carrera is remote and the weather is fickle — calm days are the prize.
10. Fingal’s Cave, Scotland
A sea cave on the uninhabited island of Staffa, made entirely of hexagonal basalt columns — the same geology as the Giant’s Causeway, just flooded by the sea. The acoustics inspired Mendelssohn to write an overture about it. Boats run from Mull in summer; on a calm day you land and walk in along a ledge above the swell.
11. Hang En & the show caves of Mulu, Borneo, Malaysia
Gunung Mulu’s caves are a UNESCO marvel — Deer Cave’s mouth is one of the largest cave passages anywhere, and at dusk millions of bats pour out of it in a ribbon that takes nearly an hour to empty. You walk in on boardwalks; the bat exodus you watch from outside. It is, genuinely, one of the great wildlife spectacles, full stop.
12. Eisriesenwelt, Austria
The largest ice cave in the world, in the Alps near Salzburg. You walk through chambers of natural ice formations — frozen waterfalls, glassy curtains, towering ice walls — carrying a carbide lamp, with no electric lighting in the ice section. It’s freezing inside even in August (that’s the point) so dress warm and accept the steep mountain approach to reach it.
Quick comparison
| Cave | Country | How you go through | Highlight |
|---|---|---|---|
| Waitomo | New Zealand | Boat | Glowworm ceiling |
| Blue Grotto | Italy | Rowboat | Electric-blue water |
| Škocjan | Slovenia | Walk | Underground canyon |
| Phong Nha | Vietnam | Walk + boat | Giant chambers |
| Reed Flute | China | Walk | Lit reflections |
| Benagil | Portugal | Swim / kayak | Roof skylight |
| Antelope | USA | Walk | Light beams |
| Cango | South Africa | Walk | Dripstone halls |
| Marble Caves | Chile | Boat | Blue marble swirls |
| Fingal’s | Scotland | Walk in | Basalt columns |
| Mulu (Deer) | Malaysia | Walk | Bat exodus |
| Eisriesenwelt | Austria | Walk | Ice formations |
FAQ
Do I need to be fit or brave for these? Mostly no. Glowworm boats, lit show caves, and sea grottoes are easy. Only the “adventure” routes (Cango’s crawls, blackwater rafting) and the big Vietnamese expeditions ask real fitness or nerve. Pick your lane.
What should I always bring underground? A layer (caves are cold and steady year-round), proper shoes with grip — it’s wet and slick down there — and patience for the booking caps. The good ones limit numbers and they fill.
Walk, swim, or boat — which is best? The boat-through caves win for sheer wonder; gliding in the dark hits different. But swimming into Benagil at dawn is the one I’d do again tomorrow.
Go down. The most astonishing rooms on Earth don’t have a view of the sky, and that’s exactly why most people miss them.
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