One more place to enjoy near Hilo in Hawaii
Kaumana Caves is a compelling underground lava tube system located approximately four miles west of downtown Hilo on the eastern slope of Mauna Loa. This natural wonder was created during the 1881 Mauna Loa eruption, when molten lava carved a network of subterranean passages stretching for miles beneath the lush rainforest surface. The caves open to the public as a free and accessible attraction at Kaumana Caves Park on Kaumana Drive, offering visitors a rare opportunity to explore the volcanic underworld that has shaped the Hawaiian Islands for millions of years.
The lava tube network took shape when a massive 1881 eruption from Mauna Loa sent rivers of molten lava flowing downslope toward Hilo. As the surface lava cooled and hardened, the insulated interior remained hot and fluid, eventually draining out and leaving behind the hollow lava tube system that visitors explore today. The 1881 flow came within a mile of Hilo before cooler temperatures and shifting eruption patterns halted its advance, sparing the town from what would have been a catastrophic lava inundation. The Native Hawaiian understanding of volcanic caves like Kaumana is intertwined with the traditions surrounding Madame Pele, the revered goddess of volcanoes whose spirit is believed to dwell within Halemaumau Crater at the summit of Kilauea.
Descend the steep concrete staircase at Kaumana Caves Park to enter a dramatically different world where temperatures drop sharply and sunlight fades into darkness within the first few yards of the entrance. Bring a powerful flashlight or headlamp for each member of your party, as the lava tube interior receives no natural light beyond the entrance and the terrain beneath your feet is uneven, rocky, and often slick with moisture. Visitors can explore the first quarter mile of the lava tube comfortably, navigating over fallen boulders and around ancient lava formations that reveal the geological history of the flow. The cave system extends for approximately 25 miles according to geological surveys, though the public portion accessible from the park entrance narrows and becomes more challenging after roughly 300 yards.
The entrance chamber is the most visually dramatic section, where a cathedral-like opening framed by dense tropical rainforest and towering tree ferns gives way to the dark, mysterious passage beyond. The lava formations visible on the walls and ceiling include lava stalactites, delicate drip-like protrusions that formed when molten lava dripped and cooled from the ceiling, as well as levees and flow lines that trace the path of the retreating lava river. These formations tell the story of the 1881 eruption in a way that feels far more immediate than any written account. Beyond the entrance, the cave floor transitions from jagged a’a lava, characterized by sharp, blocky surfaces, to sections of smoother pahoehoe lava that formed when the outer crust of the flow remained intact while the liquid interior drained away.
Skylights and collapsed sections along the route overhead allow intermittent shafts of daylight to filter through, illuminating sections of the lava tube in dramatic geometric patterns and revealing the fragile tree roots that dangle from the ceiling above. These skylights have allowed native ohia trees and ferns to establish themselves within the cave, creating a unique ecosystem where surface vegetation and subterranean geology intersect in unexpected ways. Photography enthusiasts will find compelling compositions throughout the cave entrance, where tropical vegetation frames the dark opening and long-exposure photographs capture the interplay of artificial light across textured lava surfaces.
Kaumana Caves serves as the starting point for exploration through the surrounding Kaumana Forest Reserve, including trails that wind through a landscape of ironwood trees, bamboo groves, and native ohia lehua forest. The area immediately around the cave entrance offers picnic tables and a grassy clearing where families and groups can gather before or after their underground adventure. The cool tropical air that vents from the cave entrance creates a uniquely pleasant microclimate that provides welcome relief on warm Hilo afternoons. The broader Saddle Road corridor connects Kaumana Caves to several other outstanding destinations along the slopes of Mauna Kea and Mauna Loa, including hiking areas and scenic overlooks that make for a full day of island exploration.
Nearby Rainbow Falls, located just three miles east of Kaumana Caves along the Wailuku River, makes an excellent companion destination for a morning or afternoon excursion. The 80-foot waterfall, known for the rainbows that form in its mist during morning hours, is surrounded by a small county park with viewing platforms and walking paths. The falls and caves together offer a complementary experience of Hilo’s water and lava features within a single compact itinerary. For geology enthusiasts, Kaumana provides the most accessible lava tube experience on the windward side of the Big Island, offering a rugged self-guided adventure that rewards preparation with a genuine sense of volcanic discovery.
Kaumana Caves is accessible year-round, with the most comfortable exploration conditions occurring during the drier months from May through September when Hilo receives comparatively less rainfall. While the lava tube interior remains cool and protected from weather regardless of surface conditions, a wet approach trail and slippery staircase can make the descent more difficult during Hilo’s frequent rain showers. Morning visits are recommended, as the park receives fewer visitors early in the day and the angled morning sunlight filtering through the skylights creates the most photogenic interior lighting conditions. Flashlights and headlamps are essential equipment regardless of season, and visitors should bring a backup light source in addition to their primary illumination. Sturdy closed-toe shoes with good traction are mandatory for navigating the uneven, often slick volcanic rock surfaces inside the cave.