Ape Cave is a 2-mile-long lava tube formed 2000 years ago by a lava flow that followed a deep watercourse. It's the longest lava tube in the western hemisphere. Hikers can walk and scramble the length of Ape Cave on either the 0.8-mile Lower Ape Cave Trail or the 1.5-mile Upper Ape Cave Trail, which requires a certain amount of scrambling over rock piles and narrower passages.
The trail eventually exits at the upper entrance. You can bring your own light source or rent lanterns for $5 at Apes' Headquarters , located at the entrance to the caves, and tag along with the free ranger-led explorations offered several times a day in summer.
Another interesting side trail is the 0.6-mile wheelchair-accessible Trail of Two Forests, on a boardwalk across a 1900-year-old lava flow that once buried an ancient forest.
