The Waimano Tunnels Hike is a unique underground adventure featuring a series of dark, abandoned tunnels deep in Waimano Valley. Originally built as part of a government water system, these tunnels now offer an eerie, off-the-beaten-path experience for those looking for something different than the usual ridge or waterfall hikes. Some sections require crawling or squeezing through narrow spaces. Can be dark inside so headlamps or strong flashlights are a must. Some tunnels have standing water. The hike begins at the Manana Trailhead in Pacific Palisades, Pearl City. The first part of the hike follows the Waimano Valley Trail, passing through lush jungle and small stream crossings. Look for a hidden, unmarked tunnel entrance along the valley floor, GPS navigation is recommended. Mid-Hike: The first tunnel is wide and walkable, but some later sections require crawling or crouching. Expect cool, damp air and dripping water from the tunnel ceilings. Certain areas are reinforced with concrete, while others are raw, carved rock. Some tunnels lead to small underground chambers or unexpected exits into dense jungle. The deeper you go, the more narrow and eerie the tunnels become. Some sections contain standing water, so waterproof boots or sandals are helpful. Descent & Return: After exploring the tunnels, retrace your steps back to the Waimano Valley Trail. The full hike takes about 2 to 3 hours round trip, depending on how much time you spend in the tunnels.