Hawaii’s coolest free attraction isn’t a beach — it’s an ancient lava tube you can stroll in

Mauna Loa’s underground tunnel awaits you

Four miles from downtown Hilo on Hawaii’s Big Island, a lava tube drops straight into the earth and keeps going for over two miles.

Kaumana Caves State Park sits right off the road, costs nothing to enter, and most people on the island have never heard of it.

The tube formed during an eruption of Mauna Loa in 1881 and ranks as the 57th-longest lava tube on the planet. You can spend 15 minutes here or lose an entire afternoon underground.

The darkness decides how far you go.

Lava crept toward Hilo for nine straight months

In November 1880, Mauna Loa, one of the largest volcanoes on Earth, erupted from its northeast rift zone and sent lava flowing toward Hilo. The molten rock moved slowly but burned through forests for nine months.

As it traveled, its outer layers cooled and hardened into a crust while hot lava kept rushing underneath. When the eruption finally ended, the lava drained and left behind a long hollow tunnel.

The flow stopped about a mile and a half from Hilo Bay.

According to Hawaiian tradition, Princess Ruth Ke’elikolani traveled to the lava’s edge, chanted prayers, and made offerings to Pele, the volcano goddess.

Sunlight pours through a collapsed ceiling

You enter through what geologists call a skylight, a section of the tube’s ceiling that collapsed long ago. A steep concrete staircase with a metal handrail takes you down into the opening.

Sunlight fills the first stretch of the cave, and the walls around you drip with ferns, philodendron, and hanging roots. Hilo’s constant rain keeps everything green and mossy year-round.

At the bottom of the stairs, the tube splits in two directions, and each one gives you a completely different experience underground.

Stand up straight inside the right tunnel

Most people head right, and it makes sense. The opening is larger, the ceilings reach 16 to 18 feet in some spots, and you can stand upright for much of the way. Sunlight fades fast, though.

Within about 300 feet, you hit total darkness. The air turns cool, damp, and still, a relief from the tropical heat above.

Beneath your feet, smooth pahoehoe lava covers the floor, though fallen rocks make parts of it uneven. This tube stretches close to two miles before it reaches private property.

Duck and squeeze through the left passage

The left side looks like a dead end at first. A narrow gap in the rock says otherwise.

You may need to duck and squeeze under a low shelf to push through, but beyond that tight spot, the passage opens into a tall, narrow tunnel.

It winds underground and ends at another collapsed section where daylight streams in from above. This route runs shorter than the right side but feels more adventurous because of the tight spaces.

If you want a hands-on caving experience, this is the one to take.

Touch the textures left by flowing lava

Inside the caves, the walls tell the story of what happened here. Smooth, flowing textures line sections where molten lava once moved like a thick river.

Lava stalactites hang from the ceiling, formed when dripping lava cooled and hardened in place. Other stretches of wall run rough and jagged, shaped by gas bubbles that got trapped in the cooling rock.

Red, orange, and yellow mineral deposits stain parts of the walls.

Above you, roots of native ohia trees dangle through cracks in the ceiling, reaching down toward the cave floor, looking for water.

No lights, no paths, no tour buses here

If you have been to the Thurston Lava Tube in Hawaii Volcanoes National Park, forget everything about it. Thurston has electric lights, flat floors, and crowds pouring off tour buses.

Kaumana has none of that. No lights. No paved walkways. No guided tours. You bring your own gear and go at your own pace, and you may have the entire cave to yourself.

The darkness, the silence, and the rough terrain give you a real sense of exploration that the polished Thurston experience just cannot match.

Pack a headlamp and tough shoes

A strong flashlight or headlamp is not optional here, because there is zero lighting inside the caves. Bring a backup light too, in case the first one dies.

Sturdy closed-toe shoes with good grip matter, because lava rock can be slippery and sharp at the same time. Long pants and a hat help protect against bumps and scrapes from low ceilings.

The cave floor gets wet and muddy after rain, and some sections can flood during heavy downpours. If the rain is coming down hard, stay near the entrance.

A rainforest grows inside a rocky crater

Before you even step underground, the surface around the entrance pulls you in. The collapsed skylight has turned into a miniature rainforest tucked inside a rocky crater.

Tree ferns, wild ginger, and thick tropical plants crowd the opening. Vines and roots hang over both cave entrances and frame them in green.

The park sits along Kaumana Drive, which connects Hilo to the western side of the island.

A small parking lot and a simple brown sign are all that mark the spot, and you can easily drive right past without noticing.

Rainbow Falls drops 80 feet into mist

Just a short drive from the caves, Rainbow Falls sits inside Wailuku River State Park.

The waterfall drops about 80 feet into a wide pool below, and on sunny mornings, rainbows form in the mist that the crashing water throws up. That is exactly how the falls got their name.

In Hawaiian, they are called Waianenue, meaning “rainbow water.”

Behind the falls sits a large lava cave that Hawaiian tradition says was the home of Hina, the moon goddess. A viewing platform waits just a short walk from the parking area.

Bubbling pools and 200 vendors in downtown Hilo

Upstream from Rainbow Falls, the Boiling Pots line up along the Wailuku River as a series of terraced pools. When the river runs high, the water churns and bubbles through them, which is how they got their name.

Downtown, the Hilo Farmers Market packs over 200 vendors into one spot on Wednesdays and Saturdays. The market has been running since 1988 and sells tropical fruits, flowers, handmade crafts, and local foods.

Over on Banyan Drive, Liliuokalani Gardens spreads out as a Japanese-style garden right along Hilo Bay.

Go underground where Hawaii was built by fire

Kaumana Caves gives you something most Hawaii attractions do not: a raw, unscripted adventure with no entrance fee. The caves connect you directly to the volcanic forces that built these islands.

You can spend 15 minutes poking around the entrance or spend hours pushing deeper into the darkness.

Pair it with a day of waterfalls, gardens, and the farmers’ market in Hilo, and you have a full day that goes well beyond the beach. The lava tube delivers a side of Hawaii most travelers never see.

Explore Kaumana Caves State Park in Hawaii

You can find Kaumana Caves at 1492 Kaumana Drive in Hilo, near the four-mile marker on Saddle Road (Highway 200). The drive from downtown Hilo takes about 10 minutes.

Admission is free, and so is the parking lot across the street from the entrance. The park stays open during daylight hours and has restrooms and picnic tables on site.

Bring flashlights, sturdy shoes, and water.

Use caution when crossing the road from the lot to the cave entrance, because the curve limits your view of traffic.

This article was created with AI assistance and human editing.

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