Nāhuku, also known as Thurston Lava Tube, is a walk-through lava cave in Hawaiʻi Volcanoes National Park. A rainforest path leads to the entrance of this roughly 500-year-old tube. The passage is lit from 8 a.m. to 8 p.m., though the floor can be wet and uneven. Parking nearby is limited, especially during the busiest part of the day.