A truly fantastic hike! The pipiwai trail hike is located in the Haleakala National Park at Oheo Gulch. It is a 4 mile round trip hike up a valley to a 400' water fall with many great sites along the way. It is well marked and has board walks and steps to make this moderate trail easier. You will be going up about 700-800 feet in elevation to get to Waimoku Falls at the end of this beautiful valley. About 1/2 mile in you will come to the Makahhiku falls overlook which is good only depending on the amount of rainfall. Another 1/2 mile and you will come to a great old banyon tree which is nice for a short break, photo op. Along the way you will see many signs of warning about dangerous cliff drop offs and it is something to step up close to the cliff to see the hundreds of feet drops down the valley to the stream below, but the trail is safe and well marked and safe to hike so don't be worried by that. Keep heading up the valley a little farther and you will start getting into the bamboo forest and the metal bridges that cross the gap twice along the way. A boardwalk makes these muddy areas no problem through this surreal forest, and makes a wind chime sound as the wind blows the bamboo into each other, Nice. When you come out of the forest will need to cross the stream a couple of times by boulder hopping and it opens up to a great waterfall with surrounding 400 foot sheer walls....really something to see, and a great reward before heading back down the valley to the parking lot for Oheo Gulch which is another 1/2 mile circle that is a must do. The whole hike will take 3 to 4 hours depending on how many stops you make, and get there early before the day trippers get there. It is great to have the trail and the falls all to yourseves. Recommended.